Here is a situation that plays out every summer in workplaces around the world.
It gets hot. Workers start removing PPE — or adjusting it, loosening it, leaving parts of it off. Management responds by reminding everyone of the PPE policy. Workers respond by complying just enough to avoid the conversation. The actual hazard exposure quietly increases.
And nobody calls it a heat stress problem. Because officially, the PPE is being worn.
The Hidden Hazard Inside the Protection
PPE is designed to keep hazards out. The trade-off is that it also keeps heat in.
The human body regulates temperature primarily through sweating. Sweat evaporates from skin, carrying heat away from the body. PPE — particularly coveralls, chemical suits, gloves, and respiratory protection — disrupts this process. It traps heat against the body, prevents sweat from evaporating, and significantly increases the metabolic cost of any physical work.
The result is that workers wearing full PPE in warm conditions are doing two jobs simultaneously: the actual task, and thermoregulation against an obstacle.
Core body temperature rising above around 38°C signals heat strain. Above 40°C is a medical emergency. And the progression from "warm" to "in danger" can happen faster than people expect, particularly when the work is physically demanding and the PPE is occlusive.
Heat stress is not discomfort. It is a physiological hazard with real consequences: heat exhaustion, heat stroke, cognitive impairment, and — in severe cases — death.
What Makes PPE Worse in the Heat
Not all PPE creates equal heat burden. Understanding the factors helps with smarter selection and risk management.
Impermeability
Chemical protective suits, particularly those made from impermeable materials like Tychem or coated fabrics, are the worst offenders. They seal the body almost completely from air exchange. The worker inside is essentially in a small greenhouse.
Even lighter, breathable protective clothing adds thermal burden compared to normal workwear — just significantly less than impermeable suits.
Respiratory protection
Full-face respirators and powered air-purifying respirators (PAPRs) add heat load around the face, increase breathing effort, and can cause significant discomfort in warm conditions. This discomfort is one of the primary reasons workers loosen, remove, or fail to achieve a proper seal with respiratory protection during hot periods.
Powered respirators that supply airflow across the face actually help with heat stress more than tight-fitting negative-pressure masks. For long tasks in hot conditions, this is worth considering.
Gloves
Hands are one of the body's key heat dissipation routes. Gloves significantly reduce this. In very hot conditions, this matters more than most people realise.
Layering
Multiple PPE items worn simultaneously — which is normal in many high-hazard environments — compound each other's thermal effects. The result is greater than the sum of the parts.
The Risk Assessment Nobody Does
Heat stress during PPE use is a foreseeable risk. It should be in the risk assessment.
In practice, many risk assessments evaluate the chemical or physical hazard the PPE protects against, but don't evaluate the thermal hazard created by wearing that PPE in the conditions where the work actually happens.
This means the protection solution creates a new hazard that hasn't been formally assessed or controlled.
A risk assessment for PPE use in warm environments should consider:
- The thermal properties of the PPE (breathability, impermeability, coverage)
- The ambient temperature and humidity of the work environment
- The physical intensity of the work
- The duration of exposure
- Individual factors — fitness, acclimatisation, health conditions, medication
- The cumulative effect of multiple PPE items worn simultaneously
Practical Controls That Actually Work
Heat stress with PPE cannot always be eliminated. But it can be significantly reduced with genuine controls, not just reminders to drink water.
Work-rest schedules
Time in hot PPE needs to be actively managed. This means defined work periods and real rest periods — in a cooler location, with PPE removed or at least partially removed, with time to recover core temperature.
The duration of safe work periods depends on the PPE type, the temperature, the physical demand, and the individual. For impermeable suits in warm conditions, safe unprotected work time can be very short.
Acclimatisation
The body adapts to heat over time — typically 7 to 14 days of progressive exposure. Workers who are acclimatised to heat are significantly more resilient to heat stress than those who aren't. At the start of a heat wave or on returning from holiday, acclimatisation is reset.
New workers and returning workers need a managed acclimatisation period. Sending someone into a hot environment in full PPE on day one without acclimatisation is a foreseeable risk.
PPE selection for thermal properties
Where the hazard allows it, choose PPE that minimises thermal burden:
- Breathable protective clothing over impermeable where the hazard permits
- Lighter gloves where grip and dexterity requirements allow
- Cooling accessories integrated with PPE (cooling vests, ice packs in pockets)
- Powered respiratory protection rather than tight-fitting masks for long duration tasks
And regarding chemical suits specifically:
If a worker needs to wear an impermeable chemical suit and is also managing a heavy or difficult menstrual cycle — please build proper break protocols that allow them to exit the suit when needed. Toxic Shock Syndrome is a real risk when workers cannot manage sanitary products because the task doesn't allow them to get in and out of the suit. Protective clothing protocols need to account for this. Full stop.
Pre-cooling and hydration
Arriving at a hot task pre-cooled and well-hydrated extends safe working time. Cold water before work, cooling vests before donning PPE, and active cooling during rest periods all contribute meaningfully.
Hydration during work in PPE requires planning — how does someone wearing a full suit drink water? This is a practical question that needs a practical answer before the shift starts.
Individual Differences Matter
Heat tolerance varies significantly between people and is affected by:
- Physical fitness and cardiovascular health
- Degree of heat acclimatisation
- Age (older workers are generally less heat tolerant)
- Certain medical conditions and medications (including some common ones like antihistamines)
- Pregnancy
- Body composition
- Previous heat illness (which can reduce future heat tolerance)
A one-size-fits-all work-rest schedule applied to a diverse workforce is a starting point, not a complete solution. Supervisors need to be trained to recognise early signs of heat strain: excessive sweating, pale or flushed skin, dizziness, headache, confusion, or cessation of sweating (a danger sign).
And workers need to feel genuinely safe raising the alarm. A culture where admitting you're struggling in the heat is seen as weakness is a culture where people hide symptoms until it becomes an emergency.
Final Thought
When PPE makes a worker unsafe in a different way than the hazard it protects against, that is not a compliance problem.
It is a risk assessment failure.
Heat stress during PPE use is foreseeable, preventable, and serious. It deserves the same formal attention as the chemical or physical hazard the PPE was chosen to control.
Protect against the hazard. And protect against the protection.
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