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It is well known that cigarettes are the leading cause of fire deaths in the United States.1 The National Fire Protection Association (NFPA) reports that in 2011 alone, there were over 90,000 smoking-related fires, contributing to over 540 civilian deaths, 1,640 civilian injuries, and $621 million in direct property damage. However, the NFPA statistics, collected from The National Fire Incident Reporting System (NFIRS) and the NFPA annual survey, define “Smoking Materials” as lighted tobacco products (typically tobacco cigarettes). There is little to no data regarding fires caused by cannabis, or what will hereafter be referred to as marijuana cigarettes.

There are situations that occur when customers and servicemen have difficulty lighting pilots on appliances after a natural gas or propane system has been shut off or following an out-of-gas call in a propane system. The inability to light the pilot light is believed to be the result of air getting into the gas system. In some circumstances, customers or servicemen will purge the gas line in order to get the ‘‘air’’ out of the lines. Sometimes this results in flammable gas entering the structure leading to an explosion, flash fire or fire, and subsequently property damage, serious injuries, and sometimes death.

Polyethylene (PE) pipe has been used as a proven means of conveying and distributing fuel gases since the 1960s.1 In the United States and Canada, PE pipe accounts for over 90% of the natural gas distribution system and has become the de facto industry standard. Although PE pipe is so prevalent, industry codes and regulations do not allow plastic pipe to be installed within a structure as a suitable means to convey fuel gas. Therefore, a coupling or fitting is used to transition from the exterior PE pipe to the metallic pipe
associated with distribution within a structure.

Raw agricultural commodities, such as corn, soybean, rice and wheat, are typically stored in bins and silos prior to shipment. During storage, it is often necessary to protect the commodities from damage by insects and pests. A common protection method utilized is the addition of solid fumigant pellets or tablets to the commodity. One of the most common solid fumigants employed is a blend of aluminum phosphide, ammonium carbamate and other inert ingredients.

There are situations that occur when customers and servicemen have difficulty lighting pilots on appliances after the natural gas or propane system has been shut off or following an out-of-gas call in a propane system. The inability to light the pilot light is believed to be due to air getting into the gas system. In some circumstances customers or servicemen will purge the gas line in order to get the “air” out of the lines. Sometimes this results in flammable gas entering the structure resulting in an explosion, flash fire or fire, which causes property damage, serious injuries, and sometimes death.

Under certain conditions the ability of a regulator to properly regulate fuel gas pressure can be affected. If a regulator problem occurs that sends high pressure gas downstream, gas-fired equipment and system components can potentially fail, which may result in a fire or explosion. This study describes the basic construction and operation of a lever-style service regulator, the type commonly used on residential and light commercial gas systems. Then, considering the mechanics of how regulators work, problematic conditions that can produce higher than normal outlet pressures are discussed and experimentally demonstrated. These examples are then discussed with regard to actual overpressure failures observed by the authors.

Regulators and gas control valves are at the heart of gas pressure regulation. The regulators are designed to limit the pressure delivered to the gas control valves to a specified maximum, typically 1.7 kPa (7 inches water column gauge (w.c.)) for natural gas and 3.2 kPa (13 inches w.c.) for propane. The gas control valve allows gas to flow to its associated appliance burner when there is a call for operation. The gas control valve usually has internal regulation, which reduces the manifold pressure below that of the incoming pressure, typically about 0.87 kPa (3.5 inches w.c.) for natural gas and 2.5 kPa (10 inches w.c.) for propane.

The investigation of a gas-related fire or explosion typically involves testing the integrity of the gas system. Oftentimes this testing reveals one or more leaks of various sizes. The investigator must then evaluate the cause of each leak and/or its potential in contributing to the cause of the incident. Two methods commonly used to evaluate the potential causal role of a leak are full scale testing and mathematical modeling. Although full scale testing is preferred, it may be cost prohibitive and impractical. In these cases, the alternative is mathematical modeling. The question that arises with the use of a mathematical model, however, is how accurately it predicts the gas concentrations that were actually present during the incident under investigation.

Fire and explosion incidents occur far too frequently every year in the United States. They occur in residences, commercial buildings, manufacturing facilities and chemical plants alike. These incidents cause serious injury, fatality, and large dollar loss as a result of property damage and business interruption. Determining the root cause of the fire and/or explosion is important in the prevention of future recurrences, assessing liability and preparing for potential future claims. This paper addresses the role of the forensic engineer in the effective investigation of fires and explosions involving gas and flammable liquids.