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When it comes to working in confined spaces, hot environments are the new challenge that the asbestos-removal industry needs to get its head around.

I say ‘new’, but as I wrote in an earlier article, the Health and Safety Executive (HSE)’s confined space rules changed back in 2014. The changes were subtle, though, and the minimal fanfare around them has meant that, even five years on, some confined space training courses still miss much of the point.

To recap briefly, there are two triggers that together make a work area a confined space:

  1. Is the access substantially confined? Ladders, ducts, and specifically ‘enclosures for the purpose of asbestos removal’ are listed
  2. Are one or more the five proscribed hazards – fire, heat, gas or free-flowing solids or liquids – present?

In short, if the access arrangements restrict your ability to get out, or that of emergency responders to get in, and there is a risk of (frankly) sudden death, then it is a confined space, and the confined space regulations apply.

Feeling the heat

I want to focus on one of the five proscribed hazards: ‘loss of consciousness arising from increased body temperature’ – or simply, working in high temperatures. Normal body temperature is between 36.1°C to 37.2°C. If it rises above 38°C, something serious is going wrong. Heat stroke – a body temperature above 40°C -is fatal without urgent attention.

It’s important to remember that these are body temperatures – not the working environment. While humans cancool themselves when the air temperature is higher than body temperature, if they’re active, or wearing heavy clothing, much lower temperatures can prove dangerous. The same is true if there’s raised humidity – sweat is slow to evaporate when the air is already saturated.

Asbestos workers are particularly vulnerable to high temperatures, as many of the controls we introduce to address the asbestos issue make it very difficult for our bodies to deal with heat. Impervious overalls prevent effective sweating, masks stop regular hydration, and the rigmarole of exiting the enclosure is a barrier to rest periods.

Therefore, ANY asbestos enclosure where it could get hot should be considered a confined space. There are some obvious ones, such as boiler rooms and ducts with hot water or steam pipes. But there are some that come at you from the leftfield, for example any open air enclosure in the summer, along with roof voids, rooftops, soffits, contaminated land and so on.

Taking action

So what do you do? You may be able to eliminate the hazard, for example by isolating a boiler. The asbestos enclosure will still have restricted access, but as the second trigger has been removed, it is no longer confined.

Of course, there will be situations where you can’t remove the risk, and if you absolutely can’t (the client wouldn’t like it is not enough!), you need to try and reduce it. There are dozens of imaginative ways you might be able to do this depending on the source of the heat:

  • Man-made heat sources can be turned down or partially isolated
  • Over-negging – drawing lots of cool external air into the area
  • Air chillers
  • Scheduling – e.g. for summer where heating is not required, winter where temperatures are lower, or night – when the sun has set.

Even after you have reduced the temperature, the risk may remain. If so you will have to monitor it very carefully, and control the residual risk. It’s here that people often overreact, or more accurately, respond with controls which don’t address the fundamental risk.

When someone says confined space, the some consultants’ knee jerk reaction is often to introduce measures like gas detection, 15-minute escape kits, harnesses, tripods and so on. However controls are only useful if they are specific to the hazard. If the risk is pockets of poisonous gas, then this could be a good design. However, if the only proscribed hazard is heat, the escape kits could make matters worse – why carry more heavy kit during an already tough job?

If a confined space is so primarily because of a heat risk, you need to develop something different. The following are pointers and areas that you should consider when designing the project.

Designing for a hot environment


Fit and healthy is the key. Anyone unwell or recovering from an illness will be more prone to heat exhaustion and ultimately heat stroke.

Hydration – make sure that plenty of drinking water is available, and that workers drink it before and after each work period. Don’t forget the means to access it – it’s not good enough to have a tap on site if there are no cups!


Staff need to understand how to recognise early symptoms of heat stress in themselves and their colleagues. They need to know what to do if they see these signs. It’s critical to have qualified first aiders on site to be able to spot, intervene and help in these situations.

Heat stress symptoms can include any or all of:

  • Headache, dizziness and confusion
  • Loss of appetite and nausea
  • Sweating, with pale clammy skin
  • Cramps in the arms, legs and abdomen
  • Rapid, weakening breathing (and pulse)

Heat stroke has similar symptoms, but sufferers can accelerate through them very quickly to collapse.

Health Monitoring

There are ways to monitor the health of operatives, and depending on the risk assessment some or all of these should be included in the plan

  • Urine checks – if a worker is lacking hydration this is where it will show up – straw colour is good, orange is bad
  • Interview – ask how they are feeling
  • Body temperature – this should be 1°C to 37.2°C. Above 38°C is a concern, above 40°C is life-threatening. Consider routine temperature checks at break times
  • Pulse – knowing what is normal for each person (before the first shift) will give you an indication of when things change. A rapid or weakening heart beat could indicate heat exhaustion, while a full or pounding beat could be heat stroke.


We’re not just interested in temperature, but in the effective temperature – taking into account other factors that may increase the risk for workers. For that we use wet-bulb globe temperatures (WBGTs), which factor in the effects of humidity, wind speed and infrared radiation (sunlight and other heat sources) on our ability to stay cool. Fortunately, these days we use electronic WBGT meters, which meansmean we no longer have to do all the calculations ourselves. There is no maximum safe working temperature, you will have to assess the lowest you can practically get the enclosure down to – and compare to that.

Method and Design

Slow, with frequent breaks. This will mean regular transiting through the decontamination unit (DCU) and an acceptance of low productivity. Regular breaks will also allow the supervisor to monitor the workers’ condition.

The enclosure should be designed to maximise the amount of cool air introduced. Consider the case of a roof void, a common example of what’s now clearly a confined space. These are enormously hot in the summer, so avoid the temptation to block the only access with a roving head! Use the natural leakiness of the roof tiles and eaves, and reverse the air-flow.

Communication and supervision become critical where workers are exposed to immediate risks, including heat. Work plans must ensure excellent communication, and the ability for 100% external supervision. There can be no lone working, and everyone should be on the lookout for symptoms in their mates.


You can’t do much about the overalls, but you might consider cool suits and air-fed masks, which may deliver cooler external air directly to the worker.

Emergency Procedures

Review the normal ‘absolute no’ of entering a confined space to affect a rescue. This standard rule is to prevent would-be rescuers becoming another victim, brought down by the same gas, water, free-flowing solid or fire as their colleague.

With heat it’s different: in all but the very hottest environments (where frankly I’d be questioning whether you can control the risks at all), heat exhaustion has a slow build up with warning signs. Clearly there is a critical role outside the enclosure – contacting emergency services and making preparation for first aid – but once that is done, should the supervisor rule out helping the rescue? You will need to assess the risks of this, rather than blindly following the ‘standard’ rules.

You should always ask, “How will I get ‘Big George’ out of this work area?” The plan might involve trolleys or harnesses to help them walk, and if there is a vertical ascent, the infamous tripod.

First Aid

What to do? I can’t stress enough: it’s critical to have qualified first aiders on site. Ideally both within the confined space, and up top. Heat stroke is very serious and can rapidly accelerate through the symptoms to collapse. Whilst the first aid response to heat stress, exhaustion and stroke is similar, – reduce the body temperature, liquids, salts and rest. However, if there’s any suspicion of heat stroke there should be an immediate call to 999.

When the old guidance for asbestos removal at high temperatures was withdrawn all those years ago, there was nothing to replace it. Fortunately that changed in 2014 with this revision to the confined spaces regulations – it’s unfortunate that our industry awareness, and the quality of our training, is yet to catch up.

Whatever the potential hazard – fire, heat, gas, solid or liquid – confined spaces are incredibly dangerous places to work, and we should remember that the projects we design have a direct influence on the life expectancy of our teams. The risks of confined spaces need appropriate and effective controls. Merely copying and pasting them in from the last off-the-peg training course might lead to disaster.

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