How to Choose the Right Escape Mask

The age and general physical condition of the intended user population is a critical factor in selecting the appropriate product.

• By Douglas Durney
• Jul 01, 2006

SINCE Sept. 11, 2001, there has been an ever-increasing demand for civilian escape masks that are capable of protecting untrained users from chemical, biological, radiological, and nuclear (CBRN) inhalants. The anthrax attacks around the country also furthered this demand. To respond to this concern and demand for personal protection, a number of companies began to market escape mask products to the general public and other untrained user populations. Unfortunately, understanding the performance of these products and their various attributes was a very onerous task for potential end users.

As part of an overall government strategy aimed at achieving uniform standards for CBRN products, the National Institute for Occupational Safety and Health worked to develop a comprehensive standard for Air Purifying Escape Respirators (APERs). The new requirements for air-purifying escape respirator certification were developed using the concept development process and are responsive to public comments NIOSH received during three public meetings, numerous stakeholder meetings, and to the NIOSH docket. NIOSH assimilated all of this information and added additional requirements the agency determined are "necessary to establish the quality, effectiveness, and safety of any respirator used as protection against hazardous atmospheres." This standard provides a universal benchmark by which buyers can assess performance.

The APER standard addresses a wide range of product performance criteria, including, but not limited to, the following: breathing resistance, field of view, fogging, CO₂, and O₂ concentrations during human subject testing, design considerations concerning the system function, gas life requirements for various test challenge agents, particulate/aerosol canister requirements, chemical agent permeation requirements, Laboratory Respiratory Protection Level (LRPL), practical performance, donning, and environmental conditioning.

One of the more rigorous NIOSH performance requirements involves the live chemical agent testing using a SMARTMAN breathing headform. The tests are performed using the agents HD (Mustard Gas) and GB (Nerve agent) gases. These test agents are placed on the complete APER after it is installed on the special breathing headform. A small chamber is then closed, which results in the entire system being engulfed in agent vapor (liquid/vapor for HD and vapor for GB). For a specified period of time, the system is subjected to this challenge while the headform continues to "breathe." The air coming through the headform then is sampled to determine whether the system is providing the proper protection level.

Challenges in Testing
Liquid HD represents a particularly difficult challenge to many materials of construction. Companies experienced in using advanced polymeric materials for military and other demanding applications are skilled in selecting the right materials and construction techniques to address these challenges. The proper polymers (often consisting of composite laminate films) that are joined by using heat welding techniques can create an effective barrier against such materials.

Another particularly difficult challenge presented by the APER standard involves the chemical challenges for the filter. Gas life testing is performed using chemicals, called Test Representative Agents (TRAs), that represent various prevalent Toxic Industrial Chemicals (TICs) and Toxic Industrial Materials (TIMs), as well as Chemical Warfare Agents (CWAs). Although traditional military filters handle CWAs very effectively, handling TICs such as ammonia very much complicates filter design. Manufacturers meeting the standard were required to come up with new/modified filter media to address this criterion.

Submitting companies must provide test data verifying their systems meet all of the identified requirements. NIOSH then conducts its own independent testing to verify compliance. Receiving NIOSH's approval assures users that the system meets the required performance criteria.

Wearers' Concerns, Selection Factors
Despite the rigorous evaluations that NIOSH-approved escape masks undergo and with the end result being a high-performance respiratory protective unit, the use of an escape respirator by civilians could still enhance the already existing feeling of panic in emergency situations and create physiological and psychological stress. In a panic situation, untrained users become very sensitive to the changes of the normal respiratory pattern, particularly to the additional breathing resistance caused by filters, valves, etc. In many cases, the non-professional users translate these phenomena to suffocation due to exposure to hazardous contaminants.

Considering these factors, in addition to selecting a NIOSH-approved escape mask, in order to minimize the stress of wearing a respirator and enhance the effectiveness of escape operations, users must consider and examine the following factors when selecting an escape mask for their particular situations:

• Understand the physical condition of the population. The age and general physical condition of the intended user population is a critical factor in selecting the appropriate product. Individuals with respiratory ailments may be more keenly aware of changes in breathing resistance; consequently, looking for products that minimize this breathing resistance is desirable. Based on significant experience working with the Israeli civilian population, it is known that breath-assisted devices are better tolerated by civilian users and most certainly by those with respiratory ailments (e.g., asthma).
• Ensure an unobstructed field of vision. In order to reduce feelings of claustrophobia and enhance the overall comfort of the wearer, systems that offer wide, unobstructed fields of view are desirable. Better visibility allows wearers to feel more comfortable in their surroundings and to understand instructions more readily.
• Being able to recognize wearers is important. Again, to reduce feelings of stress and minimize the encumbrance of wearing a mask, systems that do not obstruct the facial features of the wearer are more desirable for the user and those around him.
• Wearers must be able to communicate. The ability to communicate in an escape scenario is extremely important, both to those providing instructions and those listening to instructions. Systems that do not obstruct the mouth of the wearer help support two-way communications in the most natural manner.
• The masks should be simple to operate. During stressful situations, users of escape masks should be able to easily don the products without having to perform a series of complicated operations, such as having to adjust nosecup straps. It should be noted that despite initial training, most escape mask wearers are not professionals and do not use a respirator on a daily basis. Accordingly, systems offering the most intuitive operation are the most desirable. Prior to purchasing a system, potential buyers should request units from the manufacturer in order to perform their own assessment of the "usability" of the product. In this manner, specific needs of the intended user population can be evaluated.

In summary, the recent standards published by NIOSH have gone a long way toward providing the buyers/users of escape masks with proper benchmarks of performance. The requirements were carefully selected, and the testing involved is rigorous. In selecting which approved system to purchase, buyers should consider the factors above to ensure their purchases meet the needs of their specific applications.

This article appeared in the July 2006 issue of Occupational Health & Safety.

This article originally appeared in the July 2006 issue of Occupational Health & Safety.