BOHS Meeting on the Thermal Environment

Working in extreme heat

We had a good turnout at the meeting today in Ellesmere Port 28 people turned up to listen to four speakers who covered a number of aspects of managing the thermal environment.

Doug Hiebert talked about how BNFL dealt with a problem at their Selafield site. Maintenance work has sometimes to be carried out in relatively high temperatures and high relative humidity and the risk is increased by the need to wear very comprehensive protective clothing to protect workers from the radiological hazards. One problem they faced when assessing the risk is that it wasn’t possible to use the usual equipment to carry out environmental measurements due to the potential for it to become contaminated.

After assessing the problem a number of measures were implemented including

• classifying the area as a “confined space” and introducing restrictions on acess based on factors that could affect an individual’s susceptibility to heat strain
• trying to schedule maintenance work during plant shutdowns
• introducing quite stringent and conservative time restrictions for work in the area
• providing cooling vests

Andrew Moore from the HSE was the second speaker. He provided a regulatory perspective but also gave some good advice on how to manage the health risks associated with work in hot environments. He stressed the importance of obtaining competent advice and effective management, ensuring that all the relevant stakeholders are involved. He illustrated his presentation with a case study where workers at a leisure pool were working in relatively high temperatures and high humidities. Although treated as a thermal comfort problem, the temperatures involved meant that the workers could be considered to be experiencing thermal stress.

I was the third speaker. Copies of my slides with notes can be viewed on Slideshare and a previous post.

The final speaker was Len Morris of the HSE who announced the formation of a BOHS Topic group on the thermal environment. Anyone interested in getting involved should contact BOHS HQ.

There are a number of good on-line information sources for anyone who’d like to find out more about managing the risks to health presented by the thermal environment, including the following

• the HSE thermal environment website
• the BOHS Technical Guide on the thermal environment andaddendum
• HSE’s guidance on heat stress

Thermal Comfort

The thermal environment is one of the traditional topic areas studied by occupational hygienists. There are two issues:

• thermal stress and strain
• thermal comfort

Excessive thermal stress means that the body has to work hard to avoid he core temperature moving outside narrow limits (37 + 2 C). If that happens we’re in a serious situation that leads to serious health effects and may be fatal. Our efforts to prevent this happening can also lead to adverse effects. This is most likely to occur in extreme environments or, sometimes, in more moderate environments where particularly heavy work is being performed or clothing is worn which prevent metabolic heat escaping.

Thermal comfort is most likely to be an issue in workplaces such as offices, but complaints or concerns can sometimes occur in manufacturing environments and other types of workplace. In this case the body is not experiencing a level of stress that it can’t cope with. There isn’t a physiological problem and ill health will not occur due to excessive thermal strain. But that encompasses a wide range of conditions. Will all of them be “comfortable”? Experience clearly shows that the answer to that is “no” !

Most occupational hygienists don’t work in industries work in high or low temperatures and so usually don’t have to deal with problems due to workers experiencing excessive heat or cold stress. However most of us, at some time or other, will be faced with a situation where workers are complaining that an environment is uncomfortable.

The BOHS is holding a Regional Meeting at Ellesmere Port tomorrow on the thermal environment. I’ll be giving a presentation on how to evaluate thermal comfort. These are the slides I’ll be using.

Thermal comfort for bohs version for slideshare notes

View more documents from Mike Slater.

Coping with extreme cold

We’re running the BOHS module M201 “Thermal environment and non-ionising radiation (including lighting)” in a couple of weeks.

One of the topics we’ll be covering is cold stress and control of risks to health from work in cold environments.

An interesting blog I’ve been following is reporting on the Catlin Arctic Survey 2010. This is a British led expedition to the Artic who are investigating how greenhouse gases could affect the marine life of the Arctic Ocean. The team will be experiencing temperatures down to -30^oC (by way of comparison, a domestic freezer is only–18º) and wind speeds of up to 40kph. There is a real risk of condition such as frostbite and hypothermia.

The expedition doctor, Martin Rhodes, or “Doc Martin”, will be posting information on the medical aspects of the trip. A short video interview with him about the hazards to the human body when operating in a polar environment is available on their website here.

Hypothermia

Working outdoors in Alaska

A recent posting on the Catlin Arctic survey blog discusses the effects of working in temperatures of below -40 degrees centigrade.

Hypothermia is the result of general cooling of the body below 35 degrees C. Early symptoms include tiredness, muscular weakness and confusion. Below 30 to 32 degrees shivering stops and unconsciousness can occur. When shivering stops there is a rapid decrease of body temperature. Death may occur at where the core temperature is around or below 28 degrees C.

The body produces heat and the harder you are working the more heat is generated. At low temperatures we are likely to lose heat to the environment, the extent of this heat loss, however, will be influenced by the amount and type of clothing being worn. Chemical protective clothing can present a particular problem. Even in cold environments it is possible to suffer heat stress and strain where heavy work is being undertaken and impervious clothing is worn which does not allow enough of the heat produced to escape. This is particularly relevant to chemical workers and emergency response personnel.

The Catlin team are pulling heavy sledges of 110 kilos each an average of 6 nautical miles a day. Their clothing is of a high standard in terms of the insulation it provides, but insulation alone is not enough to prevent hypothermia in such extreme conditions as they are experiencing. as the team Doctor notes

“All clothing can do is slow down the process of losing heat. “The only way they can keep the hypothermia at bay is to keep moving and to keep eating”.