Engine Company, SOC Specialized, Special Operations Hazmat

Pressure to Perform

Issue 8 and Volume 16.

By Peter Kirk
Market Manager, Protective Systems Division
Saint-Gobain Performance Plastics

In the fleeting moments while donning a hazmat suit during an emergency situation, it is natural for first responders to feel a sense of anxiety. A host of questions can enter the first responder’s mind while preparing to combat both known and unknown chemicals in a hazmat suit. Will I be able to maneuver myself effectively in this suit? How can I be sure the exhaust valves in my suit are working properly? How often does my suit need to be pressure tested?

The answers to these questions lie in understanding the engineering behind your protective garment. While each protective garment is engineered differently, a lot can be understood about the properties and performance of your suit by examining its exhaust valves. Taking the time to consider a suit’s valves will not only help first responders select a hazmat suit but ultimately provide peace of mind to them when in the hot zone.

What’s the Pressure?

For the purpose of this article, we will examine Level A 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 pressurizes 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, first 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. 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.

The Potential for User Error

To further understand the dynamics of air pressure within your suit, take the time to examine your suit’s exhaust valves. There are several types of technology on the market. The most common exhaust valve systems employ a small diaphragm, which seats against 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. This 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 tamperproof. To be sure your valve is tamperproof, look for a closed construction and verify with your hazmat suit manufacturer that its exhaust valves are 100 percent factory tested against inward leakage and outward flow.

Check Out Those Valves

Once you have determined the construction of your valve, take the time to examine the material from which the valve is constructed. Valve diaphragms can consist of silicone or more traditional rubber (e.g., butly), 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 use 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 your hazmat suit is ready for use through routine pressure testing. Requirements for pressure testing are specified through the National Fire Protection Association (NFPA) 1991, Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies (2005 ed.). Suits certified to NFPA 1991 must be tested annually or after each time the suit is used, whichever comes first. It is important to point out that exhaust valves requiring disassembly for pressure testing present risk for damaging the valve diaphragms’ integrity through user error. To avoid this risk, look for a suit that uses permanently sealed construction valves—they will not need to be disassembled for pressure testing.

Additionally, some models of exhaust valves, often those with traditional rubber diaphragms, require the diaphragms to be replaced every two years according to manufacturer specifications. This contributes to added maintenance and logistics during the suit’s life cycle. Be sure to check if the suit you own, or are looking to purchase, has such requirements.

Sealing It All In

While physically a small component of your suit, you can see how exhaust valves are critical components to your performance, comfort, and ultimate safety while in the hot zone. Whether you are looking to purchase a new hazmat suit or donning an old favorite, understanding the dynamics of your suit should provide peace of mind, which is something every first responder deserves.

PETER KIRK is the market manager of the ONESuit® line of chemical and biological protective products at Saint-Gobain Performance Plastics in Merrimack, New Hampshire. He is responsible for product development and marketing strategies, leveraging his technical background in protective clothing and structures. He has an MBA from Franklin Pierce College, an M.S. in marketing from Southern New Hampshire University, and a B.S. in mechanical engineering technology from the University of Maine.

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