- THE MAGAZINE
Q: We are located in the South. When performing mold remediation, the standards call for closing off the supply vents and returns located in the work area. The problem is that it can get really hot in the work area, especially in the summer. Wearing protective clothing and respirators can create a lot of heat stress for our workers. Their productivity and morale suffers as a result. How do you suggest that we control the heat related problems that may result?
A: Heat stress is without a doubt a serious safety issue that needs to be addressed for those that perform remediation services that require working in hot environments and wearing personal protective equipment.
To control air-pressure differentials and prevent contaminants from escaping the work area, it is usually recommended that the structure's HVAC system be isolated from the work area. Supply vents blowing air into an area may cause the area to become positively pressurized, while returns located in the area can directly pull contaminants out of the work area and redistribute them throughout the structure.
As you point out, closing off the supply vents and returns can result in the work area becoming very hot or, in some cases, very cold. Heat stress is not just a comfort issue. It can be debilitating and in extreme cases life-threatening. Wearing personal protective equipment (PPE) makes the increased temperature in the work area an even greater concern. The protective clothing and the respiratory protection can interfere significantly with the body's natural cooling mechanisms.
A variety of health effects can be caused or aggravated by extended exposure to heat, with consequences ranging from discomfort and reduced productivity to death. The following is a discussion about these health effects based on an excellent article, "Working in Hot Environments," posted on the Centers for Disease Control (CDC) Web site:
Transient heat fatigue is a temporary condition of discomfort and strains that result from extended exposure to heat. It can cause a reduction in productivity and coordination. Those who aren't used to working in hot environments are especially susceptible. A period of gradual adjustment to hot environments (heat acclimatization) can significantly lessen the severity of the condition.
Heat rash, also known as prickly heat, is caused when moisture can't easily evaporate from the surface of the skin, which can very easily arise when wearing PPE, as in the conditions you describe in your question. The sweat ducts become plugged, and a very uncomfortable skin rash breaks out, interfering with productivity, not to mention employee morale. Resting part of each day in a cool area and regular showering can help prevent or control heat rash.
Fainting as a result of heat exposure can be caused by continuously standing with minimal movement in hot conditions. This may cause blood to pool in the lower part of the body as a result of the body's attempt to control its internal temperature, leaving less blood available to the brain. To some degree, fainting can be prevented by moving around. Quick recovery can be accomplished by lying down.
The level of salt in the body can become diluted when you sweat and drink a lot of water, causing painful heat cramps. The muscles that you use to do the work are the ones that are most susceptible. This condition can be relieved by orally taking liquids that contain salts. A solution of one teaspoon of common salt to one liter of water, or one teaspoon of electrolyte replacement formula to one glass of water, may be consumed. This provides a quick source of salt replacement. (Note: salt tablets should only be taken when prescribed by a physician.)
According to "Working in Hot Environments," heat exhaustion "includes several clinical disorders having symptoms which may resemble the early symptoms of heat stroke. Heat exhaustion is caused by the loss of large amounts of fluid by sweating, sometimes with excessive loss of salt. A worker suffering from heat exhaustion still sweats but experiences extreme weakness or fatigue, giddiness, nausea, or headache. In more serious cases, the victim may vomit or lose consciousness. The skin is clammy and moist, the complexion is pale or flushed, and the body temperature is normal or only slightly elevated."
Treatment for heat exhaustion usually involves drinking lots of liquids and resting in a cool place. Depending on the severity of the case, recovery may be quick or take several days. There are no known permanent effects. Citing again from "Working in Hot Environments," heat stroke, "is the most serious of health problems associated with working in hot environments. It occurs when the body's temperature regulatory system fails and sweating becomes inadequate. The body's only effective means of removing excess heat is compromised with little warning to the victim that a crisis stage has been reached.
A heat stroke victim's skin is hot, usually dry, red or spotted. Body temperature is usually 105°F or higher, and the victim is mentally confused, delirious, perhaps in convulsions, or unconscious. Unless the victim receives quick and appropriate treatment, death can occur.
Any person with signs or symptoms of heat stroke requires immediate hospitalization. However, first aid should be immediately administered. This includes removing the victim to a cool area, thoroughly soaking the clothing with water, and vigorously fanning the body to increase cooling. Further treatment at a medical facility should be directed to the continuation of the cooling process and the monitoring of complications which often accompany the heat stroke. Early recognition and treatment of heat stroke are the only means of preventing permanent brain damage or death."
As you can see, the consequences of excessive heat exposure can be extremely serious. So how can you protect your workers?
As with any other hazard, there are basically two approaches to protecting workers. The first consists of engineering controls, work practices and administrative controls that reduce or eliminate the employee's exposure to the hazard. The second involves personal protective equipment (PPE) that protects the employee against the hazard that could not be eliminated by the first approach.
Engineering Controls, Work Practices and Administrative Controls for Hot Environments
Work practices and administrative controls are always preferable to devices or equipment that can fail or be misused, exposing employees to the hazard. Administrative and work practice controls might include limiting employee time of exposure to the heat by scheduling regular breaks in a cool place and providing electrolyte replacement fluids. Other examples include scheduling work at night or in the early morning, when temperatures are less extreme.
Engineering controls create conditions in which the body can shed heat more easily. This can be done in a number of ways: acceleration of air movement, reduction of latent heat (humidity), reduction of sensible heat (as indicated by the dry-bulb temperature), and reduction of radiant heat. Radiant heat gain is not normally a major issue in remediation. Increasing air movement is not a good choice for remediators, as it causes contaminants to become and stay airborne, which we are generally trying to avoid when doing mold remediation.
Reducing the humidity is a good idea, as it increases the rate of evaporation from the skin and reduces body temperature through evaporative cooling. Unfortunately, the effectiveness of this approach is severely limited by the wearing of protective clothing and other PPE.
This leaves the reduction of heat (dry-bulb temperature) as the primary form of effective engineering control for heat hazards. This can be accomplished in a number of ways and perhaps it would be a good subject for a future article.
Personal Protective Equipment (PPE) for Hot Environments
The other way to protect employees is through the use of appropriate PPE. Try to find a type of protective clothing that is more permeable to water vapor while remaining impermeable to the penetration of particles such as mold spores and fragments. Such clothing allows the body's cooling mechanisms to work more effectively.
Some respirators interfere less with the body's natural cooling system or may even directly reduce the heat load. For instance, powered-air purifying respirators (PAPRs) are much cooler than un-powered air purifying respirators (APRs). This is especially true of those PAPRs that work by means of a helmet or hood rather than a face piece. The cool air circulating around the head and face helps the body shed significant heat. Be careful, as a relatively cool breeze across the face can help you feel cooler even while your body temperature continues to climb.
Supplied-air respirators can also help to control heat-stress problems by cooling the air that is supplied to the worker. In some cases the cool air can be diverted into a vest distributing it over the torso and the rest supplied to the face piece, hood or helmet, allowing the employee to stay cool even in very hot conditions. Supplied air respirators limit employee mobility significantly and are expensive.
There are a variety of cooling vests, bandanas and headbands. Many of these systems cool the body by means of evaporative cooling, the effectiveness of which is severely limited when protective clothing is worn over them. However, there are cooling vests that are extremely effective at reducing heat stress, even when used under protective clothing. These vests basically consist of a number of pockets sewn together that hold packets of water, gel or other phase change material.
Water is a "phase-change material" that changes its phase, going from a solid to a liquid or the reverse, at 32°F (0°C). Some vests use water-filled packets, but their intense cold against your skin can be very uncomfortable. One system uses a material that changes phase at 59°F (15°C). This warmer temperature eliminates the problems associated with ice packs while still effectively absorbing heat.
Since some of the coolant packs need to be pre-frozen, it would be advisable to buy two sets of coolant packs. When the cooling capacity of the packs in the vest is exhausted, usually in about two hours, they can be switched with fresh packs that have been kept cold in an ice chest. The used packs can then be placed in the ice water, where they can recharge in about half an hour.
These vests are available for a price of $100 to $200, with extra coolant pack sets often costing about $100. Some mold remediators who have started using PAPRs and coolant vest systems have told us it has resulted in a doubling of their production rate, which is an excellent return-on-investment. (Note: Some states may have regulations involving heat stress that go above and beyond those of the federal government.)
A good overview of the issues involving heat stress and of how to protect workers against it is found at: http://www.osha-slc.gov/dts/osta/ otm/otm_iii/otm_iii_4.html.