Ian Hutcheson, market manager, Saint-Gobain Performance Plastics, explains the dynamics of air pressure within a hazmat suit in order to provide peace of mind to the user

In the moments prior to an emergency situation, it is natural for emergency responders to feel a sense of anxiety while donning a chemical protective hazmat suit. However, understanding the engineering behind the hazmat suit will go some way towards easing these fears.

While each suit is engineered differently, a lot can be understood about the properties and performance of your suit through examining its exhaust valves. Taking the time to consider a suit’s valves will not only help emergency responders to select a hazmat suit, but ultimately provide peace of mind when in a hazardous situation.

For the purpose of this article, we will examine Type-1a EN 943-1 and 943-2 certified hazmat suits, which are built for chemical and gas protection, using a self contained breathing apparatus (SCBA) for respiration. These suits can be engineered to slightly inflate using the air that is exhaled through the SCBA. The user’s exhalation pressurises the suit, creating a comfortable distance between the emergency responder and the material of the suit.

Ultimately, this design makes the suit more comfortable by decreasing the impact of the suit’s weight on the head, shoulders, and mask, which increases user mobility. While inside a suit that is slightly inflated, emergency responders are more easily able to withdraw their hands for access to radios, gauges and cloth for wiping a potentially fogged visor.

It is important to note that internal air pressure levels can vary by suit design and manufacturer. Of course, the best way to test your suit is by trying it on and checking that there is a comfortable space between your body and the suit’s material.

User error

It is important to examine the exhaust valves within a hazmat suit. The most common exhaust valve systems employ a small diaphragm which fits next to a set of holes to regulate airflow and prevent leakage of air from outside of the suit. This system, while effective, requires diligent maintenance.

Maintenance entails manually dismantling and reassembling each valve to be inspected and pressure tested. The small diaphragm technology should be used with caution as it leaves the potential for user error during the process, posing the threat of inadvertently damaging the valve’s diaphragm during testing or reassembling it incorrectly. There is typically no way to accurately verify that the valve has been reassembled correctly and will function as intended during use. This clearly poses a risk, as the first responder’s protection against inward leakage and harmful gases could be compromised.

To mitigate this risk, it is important to look for hazmat suits with exhaust valves that cannot be disassembled and do not require maintenance. Consider suits that incorporate valves of a completely sealed design. Servicing is not required on closed construction valves, rendering them tamper-proof. To be sure that your valve is tamper-proof, look for a closed construction and verify with your hazmat suit manufacturer that its exhaust valves are 100% factory tested against inward leakage and outward flow.

Check the valves

The material from which the valves are made also needs to be considered. Valve diaphragms can consist of silicone or more traditional rubber (e.g. butyl), which can cause a difference in shelf life and performance.

Depending on storage conditions, diaphragms made from traditional rubber can become compromised. Extreme temperature fluctuations and dry conditions increase that risk, making the valve diaphragms susceptible to cracking over time. For a more reliable alternative, consider exhaust valves that utilise silicone rubber diaphragms. Silicone is a strong, highly inert polymer, resistant to the effects of environmental exposure. It can be difficult to visually confirm your valve’s diaphragm material, so be sure to check with the suit manufacturer for specific information.

Pressure testing

Even with the highest quality exhaust valves, it is crucial to ensure that your hazmat suit is ready for use and, if the suit has been used before, that you carry out the recommended pressure testing before putting it back into storage ready for the next incident. 

Requirements for pressure testing vary between reusable and limited life chemical suits and between manufacturers. Type-1a suits certified to the European standard EN 943 as reusable are typically required per the manufacturer’s guidelines to be pressure tested annually or after each time the suit is used (whichever comes first). In the case of limited life Type-1a suits certified to EN 943, pressure testing guidelines also vary by manufacturer but typically they only require testing if used or fully removed from their packaging.

It is important to point out that with exhaust valves requiring disassembly for pressure testing, there is a risk of damaging the valve diaphragm’s integrity through user error. To avoid this risk, look for a suit that utilises permanently sealed construction valves as these will not need to be disassembled for pressure testing. 

In addition, some models of exhaust valves, often those with traditional rubber diaphragms, require that the diaphragm be replaced every two years due to manufacturer specifications. This contributes to added maintenance and logistics during the suit’s lifecycle, which needs to be taken into account when specifying a hazmat suit.

While physically a small component of your suit, it is clear that exhaust valves are a critical component to your performance, comfort, and ultimate safety while in hazardous situations. Whether you are looking to purchase a new hazmat suit, or donning an old favourite, understanding the dynamics of your suit should provide peace of mind, which is something very important for emergency responders.

Saint-Gobain Performance Plastics


T: 0117 938 1700