High temperature

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High temperature or fever is a symptom that the body is fighting off an infection, and is easily checked with a medical thermometer. You can reduce the temperature by using medicines in the Pain Relief Medicines For Adults section or the Pain & Temperature Relief For Children section, containing paracetamol or ibuprofen, or using aspirin for adults.

[edit] High temperature & fever

A high temperature or fever is one of the effects of infection on the body. We all get this from time to time, and it should be watched carefully, especially in children. It is very important to treat it properly, and know when it is time to see your doctor for help.

High temperature

- 37ºC (98.6ºF) is about normal body temperature

- 38.5ºC (101ºF) or over in adults, or babies under 1 year old-contact your doctor

- 39ºC (102ºF) or over in children 1 to 12 years old - contact your doctor

- 41ºC (106ºF) or above is very serious and need immediate medical attention

It is important that if you take a temperature, that you do it the right way. It is not always necessary to take someone’s temperature, but it will tell you a lot more about how ill someone is, rather than by just feeling how hot they are. Our medical thermometers are safer than glass ones to use.

There are three things you can, and should do to calm-down a high temperature:-

Do the simple things first. Drink plenty and keep cool -

- Drink plenty of liquids (not alcohol). This is very important because when we have a high temperature there is more water lost as sweat, which must be replaced by drinking more. It is especially important not to become dehydrated.

- Dress lightly. It is important to allow the body to loose this extra heat, and you will interfere with that if you wrap up too much. Keep the room at a comfortable temperature, without being too hot. Have some ventilation in the room, so it is not stuffy.

- Keep children calm. If they are bouncing around they will only warm up more. Keep them quiet. This also applies to adults and exercise.

- Use cooling products such as Children's Kool 'n' Soothe on the forehead

Use medicines properly -

- Medicines to reduce temperature are important. Use the right medicine, at the right dose, and repeat the dose in the right way.

- Use your favourite brand correctly. Paracetamol is normally the first choice, but aspirin and ibuprofen can be used according to the directions, and are equally effective.

- Dangers of overdose. Too much of any medicine is dangerous, but this is especially important for paracetamol. The main thing to watch is that you remember, or write down the number of doses you take over 24 hours, and do not take more than the recommended dose. Also be very careful not to give two medicines together which both contain the same ingredient. Paracetamol is already in a lot of medicines, and you can double up on the dose without realising it. Read the ingredients very carefully if you ever use two medicines together. Even better, check with your pharmacist first.

- Danger of underdose. Many people are worried about taking too much medicine. While it very important to be careful not to give more than the recommended dose, it is equally important to take enough for it to work. As I often say to my customers "If you don’t take it, then it doesn’t work!". Take the recommended dose. There are many times when customers have come to me, or gone to see their doctor, when a temperature has stayed high, and all they needed to do was to give the medicine properly in the first place.

If these steps fail, sponge the body with water -

- Take the right dose of medicine before sponging

- Use tepid water, which feels neither warm or cold to the touch. Fill the bath to the depth of a few inches with this tepid water, and sponge the body down with it.

- Never use cold water, as this will reduce the blood flowing through the skin, and leads to shivering. Both of these effects will keep the heat in.

- Children in particular benefit from this sponging, but they may complain about it. It really helps though.

[edit] Fever in children

Children's pain & fever

Pain and high temperature are common in babies and children, and there are a range of children's medicines to help, and it is important to use them correctly. A good medical thermometer will also let you keep an accurate check in how high a temperature is rising. Always call a doctor if the baby or child seems particularly unwell. There are also special products to help with Teething.

Temperature control in the body

The 'core temperature' means the temperature of the deep tissues of the body and in normal circumstances this is kept at a very even level by a range of automatic adjustments.

When we are too hot we increase the amount of blood flowing through the skin by opening up the tiny capillary blood vessels. This radiates away excess heat and sweating can further enhance this.

When we are too cold we shut down skin blood vessels and conserve heat within the internal organs. If necessary we can generate more heat by shivering.

Fever is part of the body's defence mechanism against viruses or bacteria. The body tries to create extra heat so that the foreign organism cannot survive. Having a temperature helps you fight illness.

Actions to reduce a fever can help make someone feel more comfortable but it is not possible, or desirable, to aim to normalise the temperature while someone is fighting off an infection.

The part of the human brain that controls body temperature is not fully developed in children. This means that a child’s temperature may rise and fall very quickly and the child is sensitive to the temperature of his or her surroundings.

One of the simplest and most effective ways to help a child with a fever feel more comfortable is to take off some of the child's clothes so heat can escape from their body more easily.

Normal temperature for a child

If you take the temperature in your child's mouth or from the ear, the normal temperature is 36-36.8ºC (97.7-99.1ºF).

Thermometers

Traditional mercury thermometers are being phased out although many are still around. Mercury is a highly toxic substance if taken into the body, which can be done through skin contact, breathing in the vapour or swallowing it.

All these risks can apply to the fragile glass thermometer if it is broken, for example by a child biting it.

If you have a mercury thermometer, check with your local council how to dispose of it safely.

Modern probe-type digital thermometers are quicker to use, more reliable and are much safer if bitten.

Taking a child's temperature

A body temperature reading can be taken from the mouth, armpit, ear, skin surface or the rectum.

Although a rectal temperature reading is the most accurate and is quite often used in hospital it is not necessary to be so precise when taking temperature readings at home. Rectal temperature reading is therefore not recommended for home use.

Rectal temperatures are the closest to 'core' temperature and are about 0.5ºC (2ºF) higher than readings taken from the mouth or ear.

Temperature readings from the armpit are not very reliable and are about 0.5ºC lower than mouth temperature.

Thermometer strips that are placed on the child's forehead are popular and give a rough guide.

Most of the time the exact level of a child’s temperature is not particularly important, unless it is very high (39ºC or over).

In practical terms the temperature reading will be enough to give an indication of whether a fever is present.

Ear temperature

If you are willing to pay for an ear thermometer, this is a very quick method and will give a read-out in seconds. Ear thermometers rely on measuring infrared (heat) radiation from the eardrum.

Other types of thermometer (such as the probe type) are not suitable for taking ear readings and must never be placed within the ear canal.

Some ear thermometers are adjustable so they can be made suitable for adults or children.

- To get a reliable temperature measurement, the thermometer must be used exactly as directed.

- When you buy the thermometer, ask the salesperson how to use it, and read the instructions carefully before you start.

- Especially with small children, ear thermometers require a steady hand to find the right spot.

- The ear canal has a natural curve, so to ensure that the thermometer is pointing towards the eardrum it may be necessary to pull the top part of your child's ear gently upwards during the reading.

- If your child has been lying with their head on a warm pillow, or has just come inside out of the cold, you will need to wait 10 to 15 minutes before the ear can provide an accurate measurement of body temperature.

Under the armpit

This method is not good for small children, since they will not stay still for long enough.

With children old enough to co-operate and keep still you need to keep the thermometer under their armpit for at least 5 minutes.

From the mouth

This method is not suitable for a young child, because they may bite the thermometer and break it.

- The thermometer is placed in the mouth, under the tongue.

- It will take two to three minutes to measure the temperature accurately.

- If your child has just eaten anything hot or cold, you will need to wait 10 minutes before an accurate temperature can be taken.

We can do if our child has a temperature

Liquids

A child with a high temperature needs more liquid than usual, because the fever will make them sweat a lot.

Make sure your child drinks plenty of liquids - a teaspoonful every few minutes, if necessary. Provided they drink plenty of liquids, it won't matter too much if they eat very little for a couple of days.

Rest

A child with a high temperature also needs rest and sleep. They do not have to be in bed all day if they feel like playing, but they must have the opportunity to lie down.

Body temperature

You do not sweat out a fever. If your child shivers while their temperature is rising, it's okay to cover them with a duvet or a blanket. But as soon as your child's temperature has stabilised and he or she starts sweating, they need to cool down.

Your child only needs to wear underwear or a nappy, which will help the heat escape from the body. Make sure their room is ventilated and cool, but not draughty.

Medicines

If you want to use medication to get the temperature down, ask your doctor or pharmacist. They will be able to tell you what to use and how much. The dosage will depend on both the age and weight of your child.

Paracetamol suspension (eg Calpol) is the usual choice and ibuprofen (eg Nurofen for children) is an alternative. Aspirin should not be given to children under 16 years of age.

Attention

Sick children are often tired and bad-tempered. They sleep a lot and when they are awake; they want their parents around all the time. They might whine and act younger than their age.

It is okay to give in and spoil a child a little when they are sick. Read to them, play with them and spend time with them. This is not the time to teach a child good manners.

A child usually recovers quickly and will go back to their old self again.

Fever critical

Look at your child and use common sense. Do they look exhausted or ill? Are they behaving differently? If the answer is yes, call the doctor. You should also call your doctor if:

- you have a young child, less than three months old, who runs a high fever.

- your child cries and cries, without you being able to comfort them, and doesn't wake up easily.

- your child has a temperature over 38ºC (101.3ºF) for more than three days.

- your child has just had an operation.

- your child doesn't seem to be getting better.

If your child experiences any of the following symptoms with a fever, call your doctor.

- Stiff neck.

- Affected by bright light.

- Hallucinations.

- Red rash or blue/purple dots or patches.

- Trouble breathing.

- Cramps.

- Continued vomiting or diarrhoea.

- Continued tonsillitis.

- Pain when urinating, or urinating more than usual.

- Other illnesses.

[edit] Effects of environment

Mechanical behavior of an oxide–oxide continuous fiber ceramic composite (CFCC) consisting of a porous alumina matrix reinforced with laminated, woven mullite/alumina fibers (NextelTM720) was investigated at 1200 and 1330 °C in laboratory air and in 100% steam environments. CFCC has no interface between the fiber and matrix, and relies on the porous matrix for flaw tolerance. Tension–tension fatigue behavior was studied for fatigue stresses ranging from 100 to 170 MPa at 1200 °C, and for fatigue stresses of 50 and 100 MPa at 1330 °C. Tensile creep behavior was examined for creep stresses ranging from 80 to 154 MPa at 1200 °C, and for creep stresses of 50 and 100 MPa at 1330 °C. At 1200 °C, the CFCC exhibited excellent fatigue resistance in laboratory air. The fatigue limit (based on a run-out condition of 105 cycles) was 170 MPa (88% UTS at 1200 °C). The material retained 100% of its tensile strength. Presence of steam caused noticeable degradation in fatigue performance at 1200 °C. Fatigue resistance at 1330 °C was poor. In creep tests, primary and secondary creep regimes were observed. Minimum creep rate was reached in all tests. At 1200 °C, creep rates were 10-8–10-5 s-1 and maximum time to rupture was 255 h. At 1330 °C, creep rates were 10-7–10-5 s-1 and maximum time to rupture was 87 h. Presence of steam accelerated creep rates and dramatically reduced creep life.

[edit] Natural effects from high temperature

Effects of ocean

There are serious concerns that ocean acidification will combine with the effects of global warming to cause major shifts in marine ecosystems, but there is a lack of field data on the combined ecological effects of these changes due to the difficulty of creating large-scale, long-term exposures to elevated CO2 and temperature. Here we report the first coastal transplant experiment designed to investigate the effects of naturally acidified seawater on the rates of net calcification and dissolution of the branched calcitic bryozoan Myriapora truncata (Pallas, 1766). Colonies were transplanted to normal (pH 8.1), high (mean pH 7.66, minimum value 7.33) and extremely high CO2 conditions (mean pH 7.43, minimum value 6.83) at gas vents off Ischia Island (Tyrrhenian Sea, Italy). The net calcification rates of live colonies and the dissolution rates of dead colonies were estimated by weighing after 45 days (May–June 2008) and after 128 days (July–October) to examine the hypothesis that high CO2 levels affect bryozoan growth and survival differently during moderate and warm water conditions. In the first observation period, seawater temperatures ranged from 19 to 24 °C; dead M. truncata colonies dissolved at high CO2 levels (pH 7.66), whereas live specimens maintained the same net calcification rate as those growing at normal pH. In extremely high CO2 conditions (mean pH 7.43), the live bryozoans calcified significantly less than those at normal pH. Therefore, established colonies of M. truncata seem well able to withstand the levels of ocean acidification predicted in the next 200 years, possibly because the soft tissues protect the skeleton from an external decrease in pH. However, during the second period of observation a prolonged period of high seawater temperatures (25–28 °C) halted calcification both in controls and at high CO2, and all transplants died when high temperatures were combined with extremely high CO2 levels. Clearly, attempts to predict the future response of organisms to ocean acidification need to consider the effects of concurrent changes such as the Mediterranean trend for increased summer temperatures in surface waters. Although M. truncata was resilient to short-term exposure to high levels of ocean acidification at normal temperatures, our field transplants showed that its ability to calcify at higher temperatures was compromised, adding it to the growing list of species now potentially threatened by global warming.

Natural gas in the marine environment

In contrast with oil hydrocarbons, which have been an object of wide and detailed ecotoxicological studies worldwide, natural gas and its components have been left outside the sphere of environmental analysis, control, and regulation. At the same time, the input of natural gas and products of its combustion into the biosphere is one of the typical and global factors of anthropogenic impact.

Below you will find information on sources and composition of natural gas in the marine environment. Click on links at the end of the page to find more information on Environmental Impact of the Offshore Oil and Gas Industry.

Composition and sources of natural gas in the water

Natural gas is closely related to crude oil. Both substances are thought to have formed in the earth's crust as a result of transformation of organic matter due to the heat and pressure of the overlying rock. All oil deposits contain natural gas, although natural gas is often found without oil. Gas hydrocarbons can also be produced as a result of microbial decomposition of organic substances and, less often, due to reduction of mineral salts. Many of these gases are released into the atmosphere or hydrosphere, or they accumulate in the upper layers of the earth's crust.

The composition of natural gas varies. It depends on the origin, type, genesis, and location of the deposit, geological structure of the region, and other factors. Natural gas chiefly consists of saturated aliphatic hydrocarbons, i.e., methane and its homologues. The deeper the location of gas deposit, the higher the number of methane homologues. In gas condensate fields, the content of methane homologues is usually considerably higher than the level of methane. In gases associated with oil, the content of methane homologues is comparable with the content of methane. Large amount of gases associated with oil is dissolved in this oil. During oil extraction, as the pressure goes down, gases come to the surface of the oil. They are released in the environment in volumes of 30-300 m3 for every ton of extracted oil. These gases give about 30% of the gross total production of combustible gases in the world. However, over 25% of this amount are flared off because of the absence of the needed capacities and equipment for gas collection and processing.

Other components commonly found in natural gas are carbon dioxide, hydrogen sulfide, nitrogen, and helium. Usually, they constitute an insignificant proportion of natural gas composition. However, in some areas, their concentrations can be considerably higher.

Besides the previously mentioned sources of natural gas (transformations of organic matter in the earth's crust, microbial decomposition of organic substances, and reduction of mineral salts), gas hydrates are another extremely promising source of gas hydrocarbons on the sea bottom. According to some estimates [Zubova et al., 1990; Kellard, 1994], the reserves of gas hydrates are an order of magnitude higher than potential recoverable gas resources of all conventional fields in the world.

From the physicochemical point of view, gas hydrates can be considered as a modification of ice that has a high content of gas. They are solid crystallized substances that look like compressed snow. Hydrates form during the interaction of many components of natural gas (methane, ethane, propane, isobutane, carbon dioxide, and hydrogen sulfide) with water under certain combinations of high pressure and relatively low temperature.

Hydrate formation usually accompanies and complicates gas and oil extraction and transportation because hydrates can accumulate on the sides of wells and pipelines and thus plug them. The methods used to overcome these difficulties include pumping different inhibitors (methanol, glycol, and solutions of potassium chloride) into the wells and pipelines, dehydrating the gas, and heating it up to temperatures higher than the temperature of hydrate formation.

Similar to oil, gas enters the environment due to both natural and anthropogenic processes. Among the major mechanisms of methane natural production in the biosphere, the decomposition of organic matter by methane-producing bacteria (e.g., Methanococcus, Methanosarica) deserves a special mention. These bacteria are able to get the energy by reducing carbon dioxide in accordance with CO2 + 4H2 = CH4 + 2H2O reaction. These processes are typical for the silt deposits of lakes and marshes and for marine sediments that are lacking in oxygen and rich in organic matter.

Microbial methane formation in the oceans is usually accompanied by sulfur reduction and the release of hydrogen sulfide. These take place inside the upper part of sediments from the seafloor surface to tens and even hundreds of meters deep. In regions with a cold and moderate climate at depths of over 500 m, methane can accumulate in a form of crystal gas hydrates. In areas with a warmer climate, some methane from shallow formations is often released from the sediments into the water column and then into the atmosphere.

Methane can appear in the marine environment not only due to microbial and biochemical decomposition of the organic substance in bottom sediments. It can also occur as a result of the natural bottom seepage of combustible gases from shallow oil- and gas-bearing structures. Such seeping has been found in the Gulf of Mexico, North Sea, Black Sea, Sea of Okhotsk, and other marine areas. This process can lead to intensive vertical flows of hydrocarbon gases from the bottom to the sea surface. Sometimes it is accompanied by gas hydrate decomposition.

Over the last 100 years, the natural processes of biogeochemical production and distribution of methane in the biosphere are under large-scale anthropogenic impact. According to some estimates, anthropogenic sources contribute as much as 40-70% of methane into the global atmospheric flow of this gas [Novozhevnikova, 1995]. Large quantities of hydrocarbon gases are released during many kinds of anthropogenic activity. These include oil, gas, and coal production and transportation, burning of fossil fuels, intensive rice cultivation, animal farming, and garbage dumping. Lately, the increased levels of methane have been found even in areas of intensive aquaculture in the coastal waters. In these areas, methane could be formed as a result of decomposition of food residuals and metabolites of cultivated water organisms.

The global consequence of all these anthropogenic impacts is the gradual increase of methane concentration in the atmosphere over the last 100 years - from 0.7x10-4% to 1.7x10-4% (in volume). Many scientists believe that gases released due to human activities have already begun to affect the earth's overall temperature and the methane anthropogenic emission is responsible for about 30% of the total warming effect. If the concentrations of methane and other greenhouse gases in the atmosphere keep increasing, global changes in climatic conditions on the earth will be noticeable in the near future.

Another component of natural gas - hydrogen sulfide - is water soluble in contrast with methane. It can cause hazardous pollution situations in both the atmosphere and the water environment. Its proportion in the composition of natural gas and gas condensate, as previously mentioned, sometimes reaches more than 20%. Pollution by hydrogen sulfide can lead to disturbances in the chemical composition of surface waters. This gas belongs to the group of poisons with acute effects. Its appearance in the atmosphere and hydrosphere can cause serious economic damage and medical problems among local population. Unfortunately, in Russia, air, soil, and water pollution by hydrogen sulfide and sulfur dioxide has been reported in a number of regions. Especially severe consequences for human health and biota have been observed in the basin of the low Volga River in the zone of development of the Astrakhanskoe gas condensate field [Ecology and impact of natural gas on organisms, 1989].

The sources of atmospheric pollution also include flaring of natural gas on the offshore platforms and onland terminals. Some estimates [Cairns, 1992] show that about 10% of total gas production and up to 30% of associated gases are burned here. The behavior and distribution of the products of natural gas flaring in the atmosphere, their removal by precipitation, and the impact on the water environment have not been studied. The same situation is true regarding gas emissions at different stages of its production, transportation, and processing.

An important anthropogenic source of gas hydrocarbons in the water environment is the offshore drilling accidents. Their environmental consequences can be very hazardous. Especially dramatic situations developed in the Sea of Asov as a result of two large accidents on drilling rigs in the summer-autumn of 1982 and 1985. These accidents caused long-term releases of large amounts of natural gas into the water accompanied by self-inflaming of the gas. During these events, the levels of methane in surface waters exceeded the background concentrations up to 10-100 times. The air samples also showed very high concentrations of methane. These accidents drastically disturbed the composition and biomass of the water fauna and caused mass mortality of many organisms, including fish and benthic mollusks. Similar incidents probably took place in other regions of the world as well. However, there are no publications on this topic available.

Another potential source of gas in the hydrosphere is damaged gas pipelines, both on the seafloor and on land where they cross over rivers and other water bodies. The causes of such damage can vary from corrosion processes to natural disasters (severe ice conditions, seismic activity, and earthquakes). It should be noted that hydrocarbon gases are piped over great distances totaling many thousands of kilometers. These pipelines cross hundreds of water bodies. Possible pipeline damages can lead to hazardous impacts on water ecosystems. The negative fisheries consequences in such cases may go beyond the limits of local scale. Regional problems can emerge if, for example, an accidental gas blowout or leakage blocks the spawning migration of anadromous fish.

Methane impact on water organisms and communities

Water toxicology of saturated aliphatic hydrocarbons of the methane series has not been developed thus far. This gap cannot be filled by available materials on the toxicity of other gaseous poisons (e.g., carbon oxide, hydrogen sulfide, and ammonia) for fish. Clear behavioral specifics of each of these gases in the water environment do not allow us to extrapolate these data to predict the biological effects of methane and other saturated hydrocarbons. However, the toxicity data on different gaseous poisons can help to reveal some general features of interaction between gaseous traces and marine organisms [Patin, 1993].

The first important feature is the quick fish response to a toxic gas as compared with fish response to other dissolved or suspended toxicants. Gas rapidly penetrates into the organism (especially through the gills) and disturbs the main functional systems (respiration, nervous system, blood formation, enzyme activity, and others). External evidence of these disturbances includes a number of common symptoms mainly of behavioral nature (e.g., fish excitement, increased activity, scattering in the water). The interval between the moment of fish contact with the gas and the first symptoms of poisoning (latent period) is relatively short.

Further exposure leads to chronic poisoning. At this stage, cumulative effects at the biochemical and physiological levels occur. These effects depend on the nature of the toxicant, exposure time, and environmental conditions. A general effect typical for all fish is gas emboli. These emerge when different gases (including the inert ones) oversaturate water. The symptoms of gas emboli include the rupture of tissues (especially in fins and eyes), enlarging of swim bladder, disturbances of circulatory system, and a number of other pathological changes.

These general features of fish response observed in the presence of any gas in the water environment are likely to be found for saturated gas hydrocarbons as well. Available materials derived from the medical toxicology of methane and its homologues support this suggestion.

Medical toxicology distinguishes between three main types of intoxication by methane:

- light, results in reversible, quickly disappearing effects on the functions of central nervous and cardiovascular systems;

- medium, manifests itself in deeper functional changes in the central nervous and cardiovascular systems and increase in the number of leukocytes in the peripheral blood; and

- heavy, results in irreversible disturbances of the cerebrum, heart tissues, and alimentary canal as well as acute form of leukocytosis.

These types most likely adequately describe the general patterns of methane effects in vertebrates. However, its features in respect to ichthyofauna remain to be studied. Fish resistance to the presence of gas at different life stages is of special interest. With most toxicants, the most vulnerable periods are the early life stages. The question of whether this general pattern is typical for saturated hydrocarbons still remains open. The importance of this issue in assessing biological effects of natural gas in the water environment is quite obvious.

During toxicological studies of different gases, including methane and its derivatives, one must take into consideration the influence of other factors (especially temperature and oxygen regime) that can radically change the direction and symptoms of the effect. In particular, increasing temperature usually intensifies the toxic effect of practically all substances on fish because of the direct correlation between the level of fish metabolism and water temperature. From the physiological perspective, this can be explained not only by the general intensification of fish metabolism but also by the increased permeability of the tissues for the poisons and increased oxygen consumption under high temperatures. Thus, toxicant concentrations that do not cause any effect under low temperatures can become lethal with increasing water temperature. This circumstance should be taken into consideration during ecotoxicological assessment of the potential impact of natural gas and other toxicants, especially when studies are conducted in high latitudes. In such regions, methane hydrates may be accumulated during the winter and dissociate during the increased temperatures in the summer. This may be followed by the releasing of free methane with corresponding environmental consequences.

Another critical environmental factor that directly influences the gas impact on water organisms is the concentration of dissolved oxygen. Numerous studies show that the oxygen deficit directly controls the rate of fish metabolism and decreases their resistance to many organic and inorganic poisons. This decrease sometimes depends more on the species characteristics and the rate of their gas metabolism rather than on the nature of the poison. From the physiological perspective, such a phenomenon is explained by the fact that the level of hemoglobin in fish blood and the rate of blood circulation through the gills increase under oxygen deficit. Clearly, such effects are of special interest when interpreting the data on fish response to natural gas in situations of significant change in the oxygen regime (e.g., during eutrophication of water bodies or seasonal and weather variations of the oxygen content).

Effects of kiln drying on the practical

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.

Environmental degradation of natural rubber

Various styles of latex gloves were oven-aged for 7, 14, and 21 days at 70°C and then subjected to tension testing per ASTM D 412. Five of seven powder-free glove styles exhibited dramatic decreases in tensile strength after 7 to 14 days at 70°C, with total decreases in tensile strength ranging from 70 to over 90% after 21 days of aging. These five styles were examination gloves that were later confirmed to be chlorinated. In contrast, a chlorinated surgical glove, a non-chlorinated examination glove, and all of the powdered gloves (examination and surgical) subjected to the same conditions exhibited total decreases in tensile strength ranging from 0 to 25% after 21 days. These results suggest that chlorination, a process commonly used in the manufacture of powder-free gloves, may have detrimental effects on the ability of natural rubber latex to retain its barrier integrity after exposure to severely elevated temperatures.

[edit] Combustion technology

High-temperature drop-tube furnace

The High-Temperature Drop-Tube Furnace (HTDTF) at Southern Research is an effective facility for both fundamental research and for screening combustion-related technologies prior to pilot-scale or slipstream testing. The HTDTF facility is shown in Figure 1 and Figure 2 shows the reactor, filter, and housing.

An S-Line solid electric tube furnace is used to heat the reactor walls externally to temperatures as high as 2000°F. The reactor itself is constructed of an incoloy metal that can withstand high temperatures and corrosive environments, without being susceptible to thermal shock. When the experiments desired require it, electric heaters are also used to preheat the incoming gases and the filter housing at the reactor outlet. Gases are metered to the reactor with precision mass-flow controllers, to produce the desired combustion stoichiometry, flow rates, residence times, and additional flue-gas components or pollutants.

The fuel is added in a variety of different methods, depending on whether the fuel is a liquid, gas, large particles, or a fine powder. Several different feeders are available for feeding powdered fuel, such as the AccuRate Series 300 and TSI 3400, and liquid fuels or slurries can be sprayed in with appropriate pumps, pressurized spraying systems, and nozzles.

Combustion residues, such as fly ash or char, are collected at the exit of the reactor on the small, candle-filter element inside the filter housing, while the gas leaving the reactor is pulled through an MKS 2030 FTIR, which measures the concentration of hydrocarbons, nitrogen and sulfur compounds, CO and CO2, water vapor, acid gases, and a variety of other important gas species. As desired, the exhaust gases are also analyzed on-line for mercury concentrations or other trace pollutants. The filter element may either be maintained at high temperature across the filter or cooled to quench reactions that might otherwise take place with the char on the filter element. Hence, the HTDTF may be used to investigate gas-phase reactions, combustion products, solid fuel reaction rates, or carbon burnout in char or ash.

Among other things, the High-Temperature Drop-Tube Furnace has been effectively used to evaluate combustion catalysts, obtain reaction kinetics of solid fuels, and to screen sorbents, reagents, or other pollution control technologies, before scaling-up testing to larger facilities.

[edit] Health effects of hot environment

The heat stress

"Heat stress" is the net (overall) heat burden on the body from the combination of the body heat generated while working, environmental sources (air temperature, humidity, air movement, radiation from the sun or hot surfaces/sources) and clothing requirements. [Reference: 2008 TLVs and BEIs: Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists, 2008. p. 217.] Other heat-related terms are at the end of this document in the Glossary of Terms.

In foundries, steel mills, bakeries, smelters, glass factories, and furnaces, extremely hot or molten material is the main source of heat. In outdoor occupations, such as construction, road repair, open-pit mining and agriculture, summer sunshine is the main source of heat. In laundries, restaurant kitchens, and canneries, high humidity adds to the heat burden. In all instances, the cause of heat stress is a working environment which can potentially overwhelm the body's ability to deal with heat.

Most people feel comfortable when the air temperature is between 20°C and 27°C and the when relative humidity ranges from 35 to 60%. When air temperature or humidity is higher, people feel uncomfortable. Such situations do not cause harm as long as the body can adjust and cope with the additional heat. Very hot environments can overwhelm the body's coping mechanisms leading to a variety of serious and possibly fatal conditions.

This OSH Answers document contains information relating to the health effects of hot environments. Please see Working in Hot Environments - Control Measures for information about the prevention and control from heat related illnesses.

The human body react to hot environment

The healthy human body maintains its internal temperature around 37°C. Variations, usually of less than 1°C, occur with the time of the day, level of physical activity or emotional state. A change of body temperature exceeding 1°C occurs only during illness or when environmental conditions surpass the body's ability to cope with extreme temperatures.

As the environment warms-up, the body tends to warm-up as well. The body's internal "thermostat" maintains a constant inner body temperature by pumping more blood to the skin and by increasing sweat production. In this way, the body increases the rate of heat loss to balance the heat burden created by the environment. In a very hot environment, the rate of "heat gain" exceeds the rate of "heat loss" and the body temperature begins to rise. A rise in the body temperature results in heat illnesses.

The body control heat gain and heat loss

The main source of heat gain is the body's own internal heat. Called metabolic heat, it is generated within the body by the biochemical processes that keep us alive and by the energy we use in physical activity. The body exchanges heat with its surroundings mainly through radiation, convection, and evaporation of sweat.

Radiation is the process by which the body gains heat from surrounding hot objects, such as hot metal, furnaces or steam pipes, and loses heat to cold objects, such as chilled metallic surfaces, without contact with them. No radiant heat gain or loss occurs when the temperature of surrounding objects is the same as the skin temperature (about 35°C).

Convection is the process by which the body exchanges heat with the surrounding air. The body gains heat from hot air and loses heat to cold air which comes in contact with the skin. Convective heat exchange increases with increasing air speed and increased differences between air and skin temperature.

Evaporation of sweat from the skin cools the body. Evaporation proceeds more quickly and the cooling effect is more pronounced with high wind speeds and low relative humidity. In hot and humid workplaces, the cooling of the body due to sweat evaporation is limited by the capacity of the ambient air to accept additional moisture. In hot and dry workplaces, the cooling due to sweat evaporation is limited by the amount of sweat produced by the body.

The body also exchanges small amounts of heat by conduction and breathing. By conduction, the body gains or loses heat when it comes into direct contact with hot or cold objects. Breathing exchanges heat because the respiratory system warms the inhaled air. When exhaled, this warmed air carries away some of the body's heat. However, the amount of heat exchanged through conduction and breathing is normally small enough to be ignored in assessing the heat load on the body.

The effects of hot environments on the body

When the air temperature or humidity rises above the optimal ranges for comfort, problems can arise. The first effects are subjective in nature - they relate to how you feel. Exposure to more heat stress can cause physical problems which impair workers' efficiency and may cause adverse health effects.

In moderately hot environments, the body "goes to work" to get rid of excess heat so it can maintain its normal body temperature. The heart rate increases to pump more blood through outer body parts and skin so that excess heat is lost to the environment, and sweating occurs. These changes impose additional demands on the body. Changes in blood flow and excessive sweating reduce a person's ability to do physical and mental work. Manual work produces additional metabolic heat and adds to the body heat burden. When the environmental temperature rises above 30°C, it may interfere with the performance of mental tasks.

Heat can also lead to accidents resulting from the slipperiness of sweaty palms and to accidental contact with hot surfaces. As a worker moves from a cold to a hot environment, fogging of eye glasses can briefly obscure vision, presenting a safety hazard.

Several studies comparing the heat tolerances of men and women have concluded that women are generally less heat tolerant than men. While this difference seems to diminish when such comparisons take into account cardiovascular fitness, body size and acclimatization, women have a lower sweat rate than men of equal fitness, size and acclimatization. Laboratory experiments have shown that women may be more tolerant of heat under humid conditions, but slightly less tolerant than men under dry conditions.

The illnesses caused by heat exposure

The risk of heat-related illness varies from person to person. A person’s general health also influences how well the person adapts to heat (and cold). Those with extra weight often have trouble in hot situations as the body has difficulty maintaining a good heat balance. Age (particularly for people about 45 years and older), poor general health, and a low level of fitness will make people more susceptible to feeling the extremes of heat.

Medical conditions can also increase how susceptible the body is. People with heart disease, high blood pressure, respiratory disease and uncontrolled diabetes may need to take special precautions. In addition, people with skin diseases and rashes may be more susceptible to heat.

Substances -- both prescription or otherwise -- can also have an impact on how people react to heat.

Heat exposure causes the following illnesses:

Heat edema is swelling which generally occurs among people who are not acclimatized to working in hot conditions. Swelling is often most noticeable in the ankles. Recovery occurs after a day or two in a cool environment.

Heat rashes are tiny red spots on the skin which cause a prickling sensation during heat exposure. The spots are the result of inflammation caused when the ducts of sweat glands become plugged.

Heat cramps are sharp pains in the muscles that may occur alone or be combined with one of the other heat stress disorders. The cause is salt imbalance resulting from the failure to replace salt lost with sweat. Cramps most often occur when people drink large amounts of water without sufficient salt (electrolyte) replacement.

Heat exhaustion is caused by loss of body water and salt through excessive sweating. Signs and symptoms of heat exhaustion include: heavy sweating, weakness, dizziness, visual disturbances, intense thirst, nausea, headache, vomiting, diarrhea, muscle cramps, breathlessness, palpitations, tingling and numbness of the hands and feet. Recovery occurs after resting in a cool area and consuming cool salted drinks.

Heat syncope is heat-induced giddiness and fainting induced by temporarily insufficient flow of blood to the brain while a person is standing. It occurs mostly among unacclimatized people. It is caused by the loss of body fluids through sweating, and by lowered blood pressure due to pooling of blood in the legs. Recovery is rapid after rest in a cool area.

Heat stroke and hyperpyrexia (elevated body temperature) are the most serious types of heat illnesses. Signs of heat stroke include body temperature often greater than 41°C, and complete or partial loss of consciousness. The signs of heat hyperpyrexia are similar except that the skin remains moist. Sweating is not a good symptom of heat stress as there are two types of heat stroke – “classical” where there is little or no sweating (usually occurs in children, persons who are chronically ill, and the elderly), and “exertional” where body temperature rises because of strenuous exercise or work and sweating is usually present.

Heat stroke and heat hyperpyrexia require immediate first aid and medical attention. Delayed treatment may result in damage to the brain, kidneys and heart. Treatment may involve removal of the victim's clothing and spraying the body with cold water. Fanning increases evaporation and further cools the body. Immersing the victim in cold water more efficiently cools the body but it can result in harmful overcooling which can interfere with vital brain functions so it must only be done under close medical supervision.

The illnesses caused by long-term (chronic) heat exposure

Certain kidney, liver, heart, digestive system, central nervous system and skin illnesses are thought by some researchers to be linked to long-term heat exposure. However, the evidence supporting these associations is not conclusive.

Chronic heat exhaustion, sleep disturbances and susceptibility to minor injuries and sicknesses have all been attributed to the possible effects of prolonged exposure to heat.

The lens of the eye is particularly vulnerable to radiation produced by red-hot metallic objects (infrared radiation) because it has no heat sensors and lacks blood vessels to carry heat away. Glass blowers and furnace-men have developed cataracts after many years of exposure to radiation from hot objects. Foundry workers, blacksmiths and oven operators are also exposed to possibly eye-damaging infrared radiation.

A possible link between heat exposure and reproductive problems has been suggested. Data from laboratory experiments on animals have shown that heat stress may adversely affect the reproductive function of males and females. Exposure of males resulted in reduced rate of conception. Exposure of females caused disruption of the reproductive cycle until they became acclimatized to heat. When animals are simultaneously exposed to heat and toxic chemicals, the influence of heat exposure seems to accelerate the chemical reactivity.

In men, repeatedly raising testicular temperature 3 to 5°C decreases sperm counts. There is no conclusive evidence of reduced fertility among heat-exposed women. There are no adequate data from which conclusions can be drawn regarding the reproductive effects of occupational heat exposure at currently accepted exposure limits.

Laboratory study of warm-blooded animals has shown that exposure of the pregnant females to hyperthermia may result in a high incidence of embryo deaths and malformations of the head and the central nervous system (CNS). There is no conclusive evidence of teratogenic effects of hyperthermia in humans. The NIOSH criteria document (1986) recommends that a pregnant worker's body temperature should not exceed 39-39.5°C during the first trimester of pregnancy.