OH&S Magazine Confined Space Feature: Addressing Heat Stress Concerns

This article originally appeared in the August 2020 edition of OH&S Magazine.

Working in confined spaces can be extremely dangerous. Workers may be exposed to mechanical and atmospheric hazards. In certain situations, the temperature cannot be controlled and workers are exposed to heat stress. The good thing is, many accidents and injuries can be avoided through the correct application of planning and the appropriate use of personal protective equipment (PPE).

What is a Confined Space?

For an area to be considered a confined space (in the U.S.) several elements must be met. First, the workplace is not designed for continuous occupation for people, but large enough for them to enter. So, while a worker may have to enter the area to perform certain jobs, the area is not designed for an employee to work there as part of the normal operating procedure on an everyday or continual basis. The space will also have limited or restricted ways for the worker to enter and exit the area. Some of the most common confined spaces include tanks, ovens, silos, storage bins, hoppers, vaults, pits, manholes, trenches, sewers, fuel/chemical tanks and equipment housings. In other words, no matter what your industry, you have the potential for requiring your employees to work in confined spaces and should be prepared.

Confined spaces are defined by their physical dimensions and/or by the hazards that may arise within the space. In the United States, OSHA differentiates between non-permit confined space and permit-required confined space or permit space.

How to Look Out for Heat Stress

If an area is considered a confined space because of the risk of heat stress, then it is important to understand the risk factors and consider them when conducting your hazard assessment and formulating your work plan. Temperatures in some confined spaces can rapidly rise and expose workers to heat stress, heat illness and even death. While the most serious of these conditions is heat stroke, other less serious illnesses can pose a threat to a worker’s well-being such as:

  • Heat exhaustion
  • Heat rash
  • Dehydration
  • Heat cramps

When planning a job, consider both the temperature outside the confined space and the temperature within the confined space, keeping in mind that the latter rises as workers give off body heat. The more physical the job, the more likely it is to raise the internal temperature quickly.

According to the OSHA Quick Card: Protecting Workers from Heat Stress[1], the risk factors for heat illness include:

  • High temperature and humidity, direct sun exposure, no breeze or wind
  • Low liquid intake
  • Heavy physical labor
  • Waterproof clothing
  • No recent exposure to hot workplaces

OSHA also advises that the following warning signs and symptoms may indicate that a worker has heat stress illness:

  • Headache, dizziness or fainting
  • Weakness and wet skin
  • Irritability or confusion
  • Thirst, nausea or vomiting

Symptoms of heat stroke:

  • May be confused, unable to think clearly or pass out
  • Collapse or have seizures (fits)
  • May stop sweating

OSHA also recommends having a plan for preventing heat illnesses and providing training for workers on the dangers of heat illness. Where applicable, both of these should be part of your work plan.

The Need for PPE

Personal protective equipment (PPE) can play a pivotal role in keeping workers safe in a confined space even though it is the last resort within the hierarchy of controls. In most cases where a rescue is needed, the minimum PPE would be an anchor, body support and connector/connected retrieval line (also known as the ABC of confined space). This makes it easier to identify a disabled worker and to pull him or her out without exposing the rescue team to the danger. Additionally, if fall hazards are present the use of a self-retracting lifeline (SRL) with retrieval would be incorporated.

Unfortunately, there is no one size fits all for PPE in confined spaces; one has to take the matter on a case-by-case basis. The process should begin with thoroughly inspecting the confined space and its surrounding environment. A proper assessment should also include employing the hierarchy of controls: start by removing any hazards and looking for safer ways to do the work. This should involve the use of heat instruments as recommended by U.S. OSHA.[2] The results may help you to determine PPE options, what types of clothing workers should wear and how to schedule work/break intervals.

Next, contain any hazards that cannot be removed. Review the rescue plan and inspect all tools and equipment for obvious signs of wear or damage that may impede rescue or slow down workers while they are working and prolong their heat exposure. This may seem like common sense, but often skipping these any of these steps can result in injury or fatality.

When the temperature and humidity within the confined space cannot be controlled through engineering methods, PPE may need to be relied upon. While there are PPE manufacturers that offer devices and clothing for lowering the chances of heat illnesses, your best defense remains a good offense: that is, recognizing the symptoms of heat illnesses and intervening before the illness occurs.

As mentioned previously, most confined space injuries do not occur from atmospheric causes, but that doesn’t mean that injuries cannot and do not happen. In cases where heat within the space is an issue, consider using a supplied air respirator with vortex cooling that can cool air up to 50 degrees.

The Importance of Training

By far the best protection a company can have is an educated workforce. According to the U.S. Bureau of Labor Statistics, two leading factors in most workplace injuries were a lack of employee training and a lack of supervisor training. This necessary training should include how to recognize a confined space and how to construct a rescue plan.

Moreover, while often cited as the least effective way of protecting workers, PPE can help save lives. It can only do this, however, if it is worn, worn properly and worn throughout the job. The best way to ensure compliance with PPE policy is to train workers in the risks posed by the job, how PPE protects them from these risks, and in the proper use, care, and storage of PPE.

Additionally, both workers and job supervisors should be trained in how to inspect PPE and what criteria to use to determine whether or not the equipment should be removed from service. It isn’t always easy to ensure that PPE is fit for use simply through a visual inspection. In other cases, PPE may seem fine for one last job, but when it comes to PPE the rule is: when in doubt; throw it out. It may even mean advising a site leader or safety manager that it might be time to have to purchase new PPE, it pays to err on the side of caution.

While appropriate PPE is important in protecting workers in confined spaces, workers should be encouraged to adopt a buddy system mentality and to remind others that the proper use of PPE isn’t just about saving the individual’s life, but it could make the difference between life or death for the entire crew.


[1] https://www.osha.gov/Publications/osha3154.pdf

[2] https://www.osha.gov/SLTC/heatillness/heat_index/pdfs/all_in_one.pdf


This article originally appeared in the August 2020 issue of Occupational Health & Safety.