Additional Uses for Chemical Warfare Agent Detectors

In the United States, Type I hazardous material (hazmat) response teams – ranked (in California’s 2009 Firescope list) as the highest level of hazmat team – are required to carry Chemical Warfare Agent (CWA) detectors to guard them against the possibility of a terrorist attack. However, since being fielded in quantity after the 1995 Sarin gas attack on Tokyo’s subway system and the 9/11 terrorist attacks against the United States, there have been almost no incidents in which they have been used to investigate actual CWA incidents in the United States itself.

Largely for that reason, neither the CWA detectors nor the first responder skill sets required to use them have received much attention. However, some CWA detectors can in fact be used for a number of other challenges that have been encountered by the nation’s first responder community. For example, by addressing toxic industrial chemical (TIC) challenges outside their traditional CWA detection role, first responders can maintain greater readiness in these detectors for use in rare WMD (weapons of mass destruction) incidents and receive higher value from their detectors during routine hazmat responses.

Perhaps the most difficult challenge in gas/vapor detection incidents is pinpointing the source of the chemical agent used. One of the leading instruments used for “sniffing” such agents is the Photoionization Detector (PID). Most responder teams use 10.6eV lamps in their PIDs and, for that reason, will not detect a number of chemicals – e.g., chlorine, methylene chloride, and formaldehyde – with ionization potentials higher than 10.6 eV. Complicating the problem is the fact that PID lamps with higher ionization potential usually are not reliable enough for field use.

Real-Life Examples: Chorine Odors & Chemical Smells

Fortunately, one Ion Mobility Spectroscopy (IMS) and multi-sensor orthogonal sensing technology has the ability to sniff for a broader range of chemicals by using a suite of sensors to “see” many of the chemicals that are not detected by the PIDs. Following are two “real-life” examples of how using this technology has allowed first responders both to see and to repair a leak when other technologies have failed:

Example 1: A fire department hazmat team received a call involving what was believed to be a chlorine odor in a local residence. The homeowner and his wife had noticed a haze in the kitchen and smelled what seemed to them to be chlorine. The hazmat team dispatched a two-man reconnaissance unit equipped with chlorine meters, pH paper, and a PID. After inspecting the residence and seeing no change in the readings, a second unit – equipped with a CWA detector that had been set to the sniffing mode – was deployed, and registered additional readings that spiked at a higher level in the kitchen. A quick check, carried out without using SCBA (self-contained breathing apparatus) gear, revealed what seemed to be a burnt electrical odor. On closer inspection the responders discovered the real source of the smell – namely, the compressor motor on the refrigerator-freezer unit in the kitchen. The homeowner had mistakenly believed that the acrid smell of burning electrical components was actually chlorine. Although the initial search took about 90 minutes, the responder team equipped with a CWA detector was able toentify the real source of the smell in only about five minutes.

Example 2: Occupants of a house reported what seemed to be a “chemical” smell. A hazmat responder entered the house carrying a five-gas monitor (including the following sensors: O2, LEL, CO, H2S, and PID), but not wearing SCBA gear. Finding nothing apparently dangerous on the first floor, he cracked the door to the basement, sniffed the air at the top of the stairs, and saw no response on his meter. However, after taking only a few steps into the basement, he encountered an odor that, in his words, “knocked me down.” A second responder – wearing SCBA gear and using a CWA detector set to the sniffing mode – located the smell in only a few minutes. It was coming from the trash, where the homeowner had disposed of the contents of a medicine cabinet. Upon further investigation, responders determined that some of the containers in the cabinet had broken, their contents had mixed, and a noxious smell was produced.

Using CWA Detectors for TIC Detection & “Routine” HazMat

CWA detectors are designed to ify different types of CWAs, but they also can be used to ify, and in some limited cases evenentify, certain relatively common TICs. One example of using a CWA detector for incidents involving TICs involved a major ammonia leak at an ice plant.

Regional as well as state hazmat teams responded, using their PIDs primarily to find the ammonia leaks and assess the exposure levels before making important decisions concerning the type of personal protective equipment (PPE) required. After sealing off the leak, the PIDs continued to read high levels of “something” else that could not immediately beentified, so the responders initially thought that perhaps there was another type of chemical leaking.

However, by using a CWA detector to find areas of higher concentration and checking those findings in a “TIC-Confirm” library, the responders determined that the high concentrations detected were actually ammonia diffusion caused by the large amounts of ice stored on the site. After the original leak was sealed, the ammonia diffused out of the ice and the CWA detector was then able to both locate and entify the precise source.

Organophosphates & Interior Ventilation

Organophosphate CWAs are chemically similar to some insecticides and, for that reason, many organophosphate pesticides may be ified in a CWA library as a “nerve” alarm. Following is yet another example of how CWA detection capabilities can be effectively used in a routine detection scenario.

A hazmat team responded to a call where the occupants of a house reported getting sick. Using their CWA detector, the team members found higher concentrations of a chemical around the perimeter of the floor, where a consistent nerve alarm occurred when the detector sniffed the areas of higher concentration. By using the CWA library and through discussions with the homeowner, responders found that the house had been treated with insecticides to counter a recent insect infestation. With the source entified, the hazmat team helped ventilate the structure and left only after additional sniffer levels indicated that the interior levels were similar to the outdoor background levels.

Although there seems to be little reason to use a CWA detector in daily first responder operations, it seems obvious that, by expanding their capabilities to encompass TIC detection, the detectors can quickly become very useful tools that first responders can rely on during their other operations. Moreover, becoming well versed in using CWA detectors on a routine basis also helps responders to be more comfortable by using them even in the unlikely possibility of a CWA-based WMD attack. In addition, many responders have found that the routine use of CWA detectors can be helpful in other incidents and events, including an indoor “air-quality” call (after application of a pesticide, perhaps).


For additional information on the above or similar incidents, click on:

Firescope California, 2009, “Firescope Standardized Hazardous Materials Equipment List”

“Are you missing something?,” visit

“‘Off-label’ uses of the CWA library in a ChemPro100” 

Is There Something Out There?

Christopher Wrenn

Christopher Wrenn is the vice president of Americas sales for AEssense Corp., a Silicon Valley developer and manufacturer dedicated to providing innovative technological solutions for plant growers worldwide. Previously, he was senior director of sales and marketing for Environics USA, a provider of sophisticated gas and vapor detection solutions for the military, first responder, safety, and homeland security markets. He was also a key member of the RAE Systems team. He has extensive experience teaching gas and vapor detection and has been a featured speaker at more than 100 international conferences. He has written numerous articles, papers, and book chapters on gas/vapor detection and received the following awards: 2011 “Outstanding Project Team Award,” in recognition of outstanding service and dedication to the Real Time Detection Registry Team presented by the AIHA (American Industrial Hygiene Association) President; 2015, received the James H. Meidl “Instructor of the Year” award at The Continuing Challenge, Sacramento, CA presented by CA State Fire Marshal; and 2016, received the “Level A Award” from the International Hazardous Materials Response Team Conference “For your Leadership Service and Support to the Hazardous Response and Training Program.” He can be reached at



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