BY JEFFREY O. STULL AND PETER A. KIRK
Standards development for the chemical protective suit industry began as the result of a 1983 accident in Benicia, California. A local hazmat team responded to a rail tank car leaking anhydrous dimethylamine for spill evaluation and control. During the response, one of the four hazmat team members noticed that the visor lens of his total encapsulated suit was beginning to crack. The team immediately exited the vapor cloud in the spill area, but not before the suit visor broke open and allowed the hazardous chemical to enter the suit and expose the team member to chemical. Fortunately, an SCBA protected the member’s respiratory system, but the individual still suffered severe dermatitis because of skin exposure.
The National Transportation Safety Board (NTSB) evaluated the accident and found that the visor material was incompatible with dimethylamine even though the suit manufacturer’s literature recommended the butyl rubber material used for most of the suit. Consequently, the NTSB formally recommended the development of specific minimum performance standards for chemical protective suits. In 1990, the National Fire Protection Association (NFPA) introduced the first comprehensive standards to address chemical protective clothing used by first responders.
Much has happened in the chemical protective clothing industry since 1983. The NFPA standards established for chemical protective suits focused the industry on specific requirements that applied to all aspects of suit design and performance. For example, when NFPA 1991, Standard on Vapor-Protective Ensembles for Hazardous Materials Emergencies, was first released, all materials used in the construction of the chemical protective suit (including the seams, visor, gloves, and footwear) had to demonstrate permeation resistance against an extensive battery of chemicals. Previously, suit recommendations were based only on the primary material used in the construction of the suit.1
More stringent minimum requirements introduced for material physical strength and durability, flame resistance, and component functionality, combined with overall ensemble performance, forced the industry to respond with new products. Although many manufacturers complained that the new standard could not be met, several different kinds of products were developed to meet NFPA 1991.
ABRASION AND FLAME RESISTANCE
The chemical protective suit products that first met NFPA 1991 used two different approaches involving different materials to meet the two requirements, abrasion and flame resistance, considered problematic for chemical protective suit development. To meet abrasion requirements, a material could either be (1) rugged such that, after abrasion, enough material would remain on the surface to maintain adequate permeation resistance or (2) a lighter weight, limited-use material that would be covered with more durable material to take the brunt of any physical wear.
Suit materials were also required to have a degree of flame resistance so that the suit would not endanger the wearer if the suit were accidentally exposed to flame or a high heat source.2 When NFPA 1991 was first issued, most chemical protective clothing materials were flammable. Some manufacturers solved this problem by creating an “over cover” of flame-resistant material, worn over the chemical barrier layer, that would protect the inner barrier layer from igniting and burning. The alternative was to use inherently flame-resistant polymer materials for the encapsulating suit itself.
Over covers. Using the first approach, several manufacturers designed an over cover to be worn on top of the encapsulating suit because the plastic and nonwoven materials used to construct these suits would easily ignite or melt. Moreover, these materials in the encapsulating suit could not maintain chemical nonpermeation requirements after abrasion without an additional physical protective layer over the primary suit barrier layer. Adding an over cover as part of the ensemble added bulk, making these products more costly and more difficult to use.
Moreover, end users could defeat the product’s NFPA 1991 compliance by not wearing the over cover. Some product distributors provided the over cover separately from the principal encapsulating suit, forcing the NFPA in subsequent editions of NFPA 1991 to specify that all products be provided to the end user in a single integrated system. Matters were made worse by the perception that the over cover was intended only for flash fire protection; many end users thought they did not need the over cover because of improved on-site flammable gas monitoring. This belief was reinforced by the fact that the over covers manufacturers supplied were made of aluminized materials.3 Often, these end users did not realize that the reason for the over cover was the fact that the primary barrier material could not meet both base abrasion and flame resistance requirements.
Single-layer materials. The second approach focused on developing more robust materials that could meet all criteria in a single layer. The material would have to withstand abrasion and still provide chemical resistance to the broad range of chemicals used for certifying suits and also be flame resistant. Generally, this involved a high degree of material engineering resulting in more robust, complex polymer products since the range of desired material characteristics could not be achieved with conventional material polymers. The materials thus developed could then be used in a single layer in vapor-protective suits and provide greater ease of movement, durability, and overall protection for multiple uses. However, these suits tended to be relatively heavy, stiffer than competitors’ products, and more expensive.
The chemical protective suit industry was divided into “single skin” vs. over cover technology. On one hand, the disposable chemical protective suit industry lost the advantage of relatively cheap products that needed a relatively expensive over cover to supplement the product to achieve NFPA 1991 compliance. In many cases, the over cover more than doubled the price of the single-layer, limited-use suit. Issues also arose regarding the limited use and disposability of suits. Hazmat teams recognized that chemical protective suits contaminated at an incident would need to be disposed of; but at the same time, they recognized that the teams would often use suits in many responses in which there was little or no exposure to hazardous chemicals.
Given the reality of exposure at hazardous materials incidents, the industry decided that protection was primarily preventive in most cases. Hence, the ensemble should provide the highest level of protection for as many threats as possible but not overly encumber the responder in performing the necessary tasks.
Later editions of NFPA 1991 added additional protection requirements to the criteria for vapor-protective ensembles. Most recently, this included taking the high-end requirements for first responder protection against chemical, biological, radiological, and nuclear (CBRN) agents from Class 1 in NFPA 1994, Standard on Protective Ensembles for First Responders to CBRN Terrorism Incidents, and making those requirements mandatory for all NFPA 1991-compliant suits.4 These new requirements endorsed the idea of a “super suit” that can singly protect first responders against a large variety of hazardous materials in a range of different missions.
SINGLE-LAYER TECHNOLOGY
Some of the initial products that followed the single-layer approach were relatively heavy and stiff and inhibited first responders’ movement. Some companies developed materials for suits that would afford a maximum level of safety in a lightweight and relatively comfortable ensemble. Such developments often took several iterations of material improvement over several years to provide new products that were lighter weight and provided greater economy. A key aspect of the new material technology was providing relatively soft and flexible materials that could meet all of the NFPA 1991 criteria, including abrasion and flame resistance, without requiring a separate over cover material.
At the same time, suit manufacturers had to address key design considerations that enabled high levels of integrity and easier use, donning, maintenance, and storage of the encapsulating suit. Suit integrity is measured in the field using an inflation test in which the exhaust valves are blocked, the suit is inflated to a specific pressure, it is allowed to relax, and then it is monitored to see if the suit will continue to hold pressure. Current NFPA 1991 criteria require that suits be inflated to five inches of water gauge pressure, relaxed to four inches of water gauge pressure but not drop more than 20 percent (less than 3.2 inches of water gauge pressure).
More robust materials and seams, together with durable closures and interfaces for reusable chemical protective suits, generally allow chemical protective suits to maintain integrity at much higher pressures. Other design features introduced provide easier donning and doffing, an enlarged back area to permit improved accommodation of SCBA, and internal belting for better overall fit and function. Additional features include a replaceable outer visor with optional tinted visor, replaceable gloves, and compressibility of the overall ensemble to require less storage space. All of these characteristics are particularly important for reusable suits to ensure their continued comfortable use and long service life.5
GLOVES
A serious problem facing the chemical protective suit industry for years has been the inability to construct gloves that allow dexterity. The glove systems are one of the weak areas of the chemical protective ensemble. Most gloves tend to be rubber to allow form fitting and good hand function. But most rubber glove materials cannot resist permeation by many of the NFPA 1991 chemicals and generally ignite easily. Although plastic film laminate gloves offer much better chemical resistance, these gloves are also flammable, offer poor physical hazard resistance (i.e., cuts and punctures), and hamper hand function.
Multiple gloves. Using multiple glove systems has been the unavoidable solution wherein plastic gloves are fitted inside rubber gloves, such as Neoprene®, which can pass flame-resistance tests, or another type of rubber inner glove is used with an Aramid-based outer glove. End users generally find these glove systems difficult to use. If a plastic laminate inner glove is used, some end users cut out the inner glove by inverting the glove and withdrawing the hand from the glove. Such practices defeat the overall hand protection the emsemble offers.
Integrated gloves. In response, the industry has created new glove products that complement some of the new suit designs. One new glove technology offers a highly integrated, layered glove instead of multiple gloves that are simply fitted inside one another. In this layering system, the outermost layer provides cut and puncture resistance and some liquid resistance over a barrier layer.
Some new gloves also provide an innermost moisture management layer for more comfort, wicking away moisture from the hands to help keep them dry during use. In these gloves, the new barrier layers provide the chemical resistance consistent with the suit material, including protection against chemical warfare agents. The new materials in all three layers of the system are all flame resistant, unlike conventional combined gloves. When tested to the NFPA 1991 requirements, the glove materials well exceed flame resistance criteria with no measured afterflame and low burn damage. All three layers provide a high degree of physical protection (i.e., resistance to punctures and cuts) that well exceeds the base NFPA 1991 requirements as well as the optional liquefied gas protection and chemical flash fire protection requirements. Most importantly, the integrated nature of the overall glove system provides a glove with all layers designed to work together to maximize fit and limit glove impact on dexterity.
More than 15 years after NFPA 1991 was introduced to address the performance of total encapsulating suits, the chemical protective suit industry has evolved to provide improved first responder protection against incidents involving hazardous materials. The evolution has included a variety of products, some better meeting first responder needs than others. Although compliance with NFPA 1991 is intended to provide first responders with vapor-protective suit ensembles that address several incident hazard types, the trade-offs in suit materials and design sometimes create problems for maintaining this compliance or affording consistent protection. Some of the newer products in the industry are intended to overcome these problems and advance the state of chemical protective ensemble technology.
Endnotes
1. In many cases today, this practice is still followed by manufacturers selling chemical protective suits that are not subject to certification against NFPA standards.
2. The flame resistance requirement in NFPA 1991 was never intended to address the use of suits in flash fire environments or where contact with flame or high heat is expected. NFPA 1991 provides separate criteria for certification of vapor-protective ensembles for escape during accidental exposure to flash fire environments that include more severe exposure criteria.
3. NFPA 1991 does not require the use of aluminized materials. There are many alternative flame-resistant materials that could be used to provide protection from abrasion and flame contact to the inner barrier layers of two-layer vapor-protective suit ensembles.
4. In previous editions of NFPA 1991, protection from chemical and biological warfare agents that might be used in a terrorism incident was addressed in optional certification criteria. Similar criteria were formerly embodied in NFPA 1994, Standard on Protective Ensembles for Chemical/Biological Terrorism Incidents.
5. Currently, NFPA 1991 requires manufacturers to declare the storage life of their chemical protective suits. This is the length of time that the suit can remain in the response team’s inventory when properly maintained and not used in training or actual incidents. Service life is the length of time that a chemical protective suit can continue to be used (for training and actual incidents) when properly maintained. Of course, it is important to note that any hazardous materials incident can require a reusable chemical protective suit to be removed from service if the suit is heavily contaminated, cannot be decontaminated, or is damaged beyond reasonable repair.
JEFFREY O. STULL is the president of International Personnel Protection, Inc. in Austin, Texas.
PETER A. KIRK is the product manager of Protective Systems for Saint-Gobain Performance Plastics, in Merrimack, New Hampshire.
