Even if the operator follows all the proper procedures, the M8A1 Alarm System may not be 100% effective—due in part to its operational design limitations or its detection sensitivity. Like all chemical warfare agent detectors, the M8A1 must balance its sensitivity (ability to sense the presence of nerve agent vapor) with its selectivity (its ability to avoid sensing chemicals other than nerve agents). Designed to provide the maximum warning time to unprotected troops, the M8A1 was designed to be very sensitive (Table 1).
Table 1. M8A1 Alarm System Detection Sensitivity[28]
Agent Class |
Agent(s) |
Detection Sensitivity (in vapor form) |
Nerve |
G Series |
0.1 mg/m3 to 0.2 mg/m3 |
VX |
0.4 mg/m3 |
Unfortunately, increasing sensitivity reduces selectivity and soldiers suffer false alarms from a number of interferents that form ionized products similar to those of nerve agents. Many chemical compounds used in either a normal or a military operational environment (i.e. diesel, gasoline exhaust, burning fuel, etc.) can cause this system to false alarm. Examples of known interferents are shown in Table 2.
Table 2. M8A1 Alarm System Interferents[29]
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Additionally, operating in unusual or severe environmental conditions for which the system was not designed could also cause false alarms. For example, during the Gulf War, high temperatures and sand concentrations often caused this system to false alarm.[30] Operating in unusual or severe conditions can drain the system’s power sources, especially the batteries. In turn, low batteries can cause a false alarm.
OBSERVATIONS FROM DESERT STORM
The M8A1 Chemical Alarm System was widely used during Desert Storm, where it encountered a decidedly hostile environment. Because of the number of M8A1 Alarm Systems used, there is considerable feedback from those who actually worked with the system:
- "...adverse operations were conducted under adverse field conditions. From the Saudi berm north, the air was heavy with oil smoke. This smoke deposited an oily residue on the alarms’ paddles which tripped the alarms. The M8A1s were useless in the smoky, dusty desert environment."[31]
- "Units instructed to keep aircraft clear of launch sites...chemical alarms alerting; chemical survey of the area produced negative results and it was determined to be a false alarm caused by emplacing the M8 too close to vehicle exhausts. Units were advised of the possibility of false alarms from the source."[32]
- "...many M43A1 Detectors (a component of the M8A1) are sounding an alarm due to heavy concentrations of sand and engine exhaust, etc. These alarms cannot be reset which results in them being turned in for high level maintenance...change TM [Technical Manual] to provide detailed instructions on operators purging of the M43A1."[33]
- "M8A1 Alarm batteries were only good for 30-32 hours in the desert environment compared to its normal 72 hours."[34]
- "Many false alarms due to a low battery caused units to unnecessarily upgrade their protective posture and may have desensitized soldiers to a real hazard. The M8A1 Alarm should have an alternate low battery alarm/signal. This would allow units to immediately identify an alarm as a low battery warning."[35]
During the Gulf War, the M8A1 Chemical Alarm System encountered many of the interferents (oily smoke, blowing sand, extreme temperatures, etc.) that cause it to false alarm. Because of the system’s sensitivity, combined with the conduct of daily maintenance during which the alarm system’s audible signal might also have been tested, the M8A1 alarms frequently sounded—so frequently that some soldiers lost confidence in the alarms, or worse, turned them off.
The M8A1 Chemical Alarm system is a useful tool for detection of chemical warfare nerve agent vapors and was used extensively by US troops during Operation Desert Storm. In order to improve troop safety and assure alerting for nerve agent vapors, the US government accepted the possibility of the increased occurrence of false alarms. Critical design considerations allowed for initial false alerts that, because of the environment of the desert, were much higher than many soldiers expected. Based on inputs from commanders and lessons learned from Desert Storm, improvements will be incorporated into the M22 Automatic Chemical Agent Detector Alarm (ACADA) in March 1998—eventually replacing the M8A1 Alarm System.[36] This new detector will sense both nerve and mustard agent vapors, and is expected to have fewer false alarm responses to many known interferents—especially gasoline and diesel exhausts.
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