Protecting Workers in High-Heat Industries

Safeguarding workers in high-heat settings with the right protective clothing involves understanding a bit about heat transfer, the work being done, and the best materials and technologies for the job.

• By Mary Ann Merikoski
• Mar 01, 2024

If you’re a safety professional, you likely come across heat hazards regularly. There is much focus these days on heat stress and exhaustion — in fact, the National Institute for Occupational Safety and Health (NIOSH) has published a recommended standard for occupational heat stress, along with a PPE standard requiring every employer in general industry to conduct a hazard assessment to determine the appropriate PPE to be used to protect workers from the hazards identified (29 CFR 1910.132(d)). 

OSHA recommendations for heat stress include proper hydration, frequent breaks, and avoiding the midday sun. But what if high heat is intrinsic to the task being performed, and the work can’t be done without it? Hot work happens in a multitude of environments, from restaurant kitchens to auto assembly plants to smelting blast furnaces. 

In the realm of hand protection, the EN407 Standard developed in Europe but recognized internationally established a rating system that, based on various component test methods, gives clear guidance on whether a product meets the requirements of a specific work environment. 

This article will share some high-level insights into the various types of heat most commonly found in industrial environments, and questions to ask as you work through the process of selecting the right protective equipment.

A (Little) Bit of Science

There are three primary ways heat is transferred: convection, conduction and radiation. 

• Convection is heat transfer through a fluid (liquid or gas). Ice melting or the heat rising over a fire are examples of convective heat transfer. 

• Conduction is heat transfer through kinetic energy that passes from adjacent particles. For example, a pot of water sitting on a hot stove burner is heated through conduction. 

• Radiation is heat transfer through electromagnetic waves. Radiant heat is heat that you feel when you are near a heat source, like when you’re sitting near a campfire.

When selecting PPE to address thermal hazards, it’s important to classify the kind of heat transfer involved as a preliminary step — especially when there are multiple types of heat in play. 

A foundry worker might spend part of their day next to a furnace bringing metals to the melting point and later pouring that molten material into molds, with the risk of molten splash. A welder might be working outside in cold weather, but still need protection from sparks and slag. 

Hazards Uncovered

Common hazards identified within the risk assessment for high-heat industries include: 

• Thermal burns from splashing hot liquids or contact with hot surfaces 

• Chemical burns from exposure to acids, caustics, flammable, and toxic substances 

• Back strains and musculoskeletal disorders from awkward positioning, improper or heavy-weight lifting, repetitive motion 

• Heat stress from the high-heat, high-humidity environment, enhanced with wearing PPE 

• Impact, crushing, or amputating injuries from manual lifting or moving of heavy materials 

These types of hazards lead to first-, second- and third-degree skin and eye burns, short-term and long-term back pain, and altered quality-of-life from significant injuries or heat-related illnesses that forever impact an injured person, his/her family, and his/her ability to work (livelihood). 

The hazards present on site and the serious consequences of inadequate protection should motivate any responsible manager to ensure adequate protection for workers. But how can you tell if your PPE is sufficient?

A Material Difference

Identifying thermal transfer type helps in selecting the right PPE. Material matters — and there are many materials available to address high-heat hazards in common industrial applications. 

• A para-aramid fiber such as Kevlar provides high heat resistance and makes for a very strong, flexible yarn.

• A meta-aramid fiber such as Nomex also provides high heat resistance, but Nomex yarns have lower tensile strength than Kevlar and tear more easily.

• Why would you ever choose Nomex over Kevlar then? Because Nomex yarns have a soft hand that tends to make softer fabrics and therefore more comfortable clothing. More comfortable means an increased likelihood of wear which means better compliance.

• And then there are fibers like OPAN, the core fiber in CarbonX fiber blends, that carbonize and expand when exposed to intense heat or flame, starving the yarns of oxygen and therefore eliminating the fabric’s ability to combust. That Limiting Oxygen Index (LOI) yields a fabric that is truly non-flammable. 

Key Questions to Ask Before Buying

So, how can you discover the best information to make a determination on which protective apparel to use in a given high-heat situation? The following questions will elicit enough information to narrow in on good options — and then you may well have to test samples in the specific environment. A good PPE manufacturer or distribution partner will work collaboratively to get to the safest, most cost-effective solution.

1. What is the average working temperature during the task? 

2. What is the maximum temperature that might be reached? How often does that happen? How long does exposure at the high temperature last?

3. Does the wearer touch the hot item (conductive heat) or just work near the heat (radiant heat)?

4. How long is usual exposure time? 

5. If the wearer is picking something up or holding something, how heavy is that object, and how long do they hold it? (The heavier the object, the more it compresses the fibers in the PPE fabric, leading to quicker heat transfer and a shorter time to pain.)

6. Is there moisture or splash involved? If so, how often and how much? What substance is the splash? (Will the wearer need chemical protection as well?)

7. Are there abrasion or cut hazards? (If so, need to choose a fabric that is more abrasion-resistant.)

8. What are the ambient air conditions in the facility — is normal heat stress an issue in addition to the high-heat hazard? 

9. And the simplest but best question of all: What are you using now? What do you like about it, and what would you like to improve? 

You Can Ask for Help

You don’t have to make this decision alone. Many vendors and suppliers have in-house safety experts on staff who can offer additional information and perspective. Some also perform on-site assessments in order to properly gauge the hazards your employees will be facing and determine the appropriate
PPE.

This article originally appeared in the February/March 2024 issue of Occupational Health & Safety.