METHYL ISOTHIOCYANATE SUSPECTED LEAK

METHYL ISOTHIOCYANATE SUSPECTED LEAK

BY STEPHEN L. HERMANN

Temperatures of 1087F complicated the handling of a suspected leak of a liquid poison after a truck driver began to feel sick while inspecting the tires during a rest stop. The driver reported that he detected a “chemical odor” at the rear door of his trailer that caused him to feel dizzy and weak. The incident occurred in late July.

THE OPERATION

Responding units secured the shipping papers for the mixed load of freight, which included several hundred pounds of methyl isothiocyanate, a liquid the U.S. Department of Transportation classifies as a poison and a flammable. (See “Characteristics of Methyl Isothiocyanate” on page 123.)

Since the driver did not see any liquid leaking from the trailer, responders attempted to open the rear trailer door and use detection instruments to check for a flammable atmosphere. The fact that there was no known liquid present led responders to conclude that a flash fire presented the most significant hazard and that firefighting turnout gear thus offered the most appropriate protection to the entry team. High-pressure, self-contained breathing apparatus (SCBA) were used with the lighter 30-minute air cylinders.

Some of the freight in the trailer had shifted during transport, The rear door could be raised only a foot or two because some of the freight in the trailer had shifted during transport. Instrument probes inserted inside the trailer did not detect any flammable atmosphere. Because of the 1087F temperature, the first crew was taken to the rest and rehabilitation area, and a second entry team was assigned the task of attempting to push the freight back so the rear door could be completely opened. The second team succeeded in raising the door all the way and removed several items of freight to permit entry into the trailer. They walked across the top of the freight in the load and reached the boxes of the flammable poison in the nose of the unit. A condensed data sheet label taped to the side of one of the boxes was used to confirm the chemical`s identity.

The entry team reported that its instruments had again indicated that the atmosphere was not flammable and that a cyanide Draeger tube had shown no readings.

The packages of the poison were found to be in good condition. No liquid was present in the trailer, and there was no apparent leak.

It was determined that the chemical odor must have come from other items in the trailer and that the driver was probably suffering from exposure to the unaccustomed high Arizona temperature.

Hazardous materials technicians from the Arizona Department of Public Safety (DPS) Highway Patrol Bureau responded to the scene. Commercial vehicle safety specialists from the unit enforce the state`s hazardous materials transportation regulations. Additionally, they act as state-on-scene coordinators (SOSCs) under the state`s hazardous materials emergency response plan. The SOSCs are trained to the OSHA 1910.120 technician level and are equipped with personal protective equipment and SCBAs. The unit also has several hazardous materials specialists, who responded to the incident and made a final inspection of the load.

The DPS team confirmed the fire department`s assessment and also used a photoionization detector, which registered readings in the 25- to 35-ppm range at the rear trailer door. However, the extremely sensitive instrument detected no readings directly around the flammable poison containers in the nose of the trailer.

A chemical odor, however, was detected from several boxes of another, unregulated chemical loaded at the very rear of the trailer. These boxes had no apparent leak but may have been impregnated with chemical residue or vapors during warehouse storage.

The freight was inspected to ensure that no other packages were possibly damaging the flammable poison boxes and that the hazardous material was properly blocked and braced within the vehicle. Following this final inspection, the vehicle was released back to the trucking company.

The driver by now had recovered from his initial symptoms. It was concluded that there had been no leak of the toxic hazardous material. The few removed packages were reloaded into the trailer, and the truck was allowed to continue on its way.

LESSONS LEARNED AND REINFORCED

Even though drivers or exposed personnel may become sick and report illness symptoms, heat-related injuries or other causes were apparently involved in this incident involving a truck load of mixed freight.

Other possibly chemically contaminated boxes in a load may cause false indications on detection instruments and complicate the determination of exactly what chemicals are involved in the incident.

High summer temperatures will severely restrict the working time of hazardous materials hot zone entry crews. Provisions must be made for significant rest and rehabilitation.

The Phoenix Fire Department deployed its “canteen” unit and a custom-built, air-conditioned rehabilitation vehicle to the incident. The canteen unit is equipped with snacks and multiple large coolers that contain water and a sports-type drink. The department has also built up a rest and rehabilitation unit that has a 25-foot-long room in which crews can get away from the heat and rest. The unit`s 20 tons of refrigeration make it possible to bring the room`s temperature down to 657F, even on the hottest days.

Multiple detection instruments and a thorough understanding of their readings are necessary when investigating suspected leaks from numerous chemical packages.

Multiple agencies, including those with enforcement capabilities involving the hazardous materials transportation regulations, may be involved even when a chemical spill is only suspected. n



(Above) To support several entries by the hazardous materials team, the Phoenix Fire Department deployed its “canteen” unit as well as a rest and rehabilitation unit with 20 tons of refrigeration. (Right) The driver of this load of mixed chemicals became sick after reporting a “chemical odor” at the rear door of his trailer while inspecting the tires during a hot July afternoon in Phoenix.

(Photos by author.)





(Top left) Since no liquid leak was apparent and the potential for a flammable vapor flash fire was recognized, hazardous materials team entry crews used firefighting turnout gear to make their reconnaissance with detection instruments. (Top right) Because of the shifting freight inside the trailer, the first entry team could open the rear trailer door only a foot or two. After several attempts to gain entry, a second entry team was constituted, and the first team was retired to rest and rehabilitation. (Bottom left) The boxes suspected of leaking the methyl isothiocyanate were located; detection instruments indicated no apparent leak of the chemical contents. (Bottom right) Following a final double check with multiple detection instruments, it was determined that no methyl isothiocyanate had been discharged. The boxes were reloaded so they could continue in transportation.


n STEPHEN L. HERMANN is hazardous materials coordinator for the Arizona Department of Public Safety and Arizona`s senior state-on-scene coordinator for hazardous materials emergency response. He is past national chairman of COHMED, the national organization of state and local hazardous materials enforcement officers, and past chairman of the Commercial Vehicle Safety Alliance Hazardous Materials Committee. Hermann has a bachelor of science degree in explosive technology and is a graduate of the U.S. Naval School Explosive Ordnance Disposal, U.S. Army Command; General Staff College; and the U.S. Army War College and is a hazardous materials specialist for his agency and a state Division of Emergency Services Hazardous Materials technical course graduate.

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