On August 10th, an explosion ignited by natural gas took place in a residential area of Baltimore, state of Maryland in the USA, destroying 3 entire rowhouses.
Further reading from CNN US: https://edition.cnn.com/2020/08/10/us/baltimore-maryland-house-explosion/index.html
These type 5 constructed homes (Type 5 is wood frame with brick veneer) were end of group to the middle, with cinderblock fire walls every other house, and still 2 fatal casualties were reported, having the last fatality been recovered late in the evening.
An active gas leak was noted on the Bravo side of the pile, the end unit. The HazMat branch of the Baltimore County Fire Department was assigned to check for gas in the surrounding houses and stopping the leak.
Area monitors (Area Raes) were placed around the perimeter, with handheld meters in the pile. In the vicinity of the gas meter (which was buried), the HazMat team was getting 60% LEL* of methane. Intrinsic PPV fans — Positive Pressure Ventilation that uses positive airflow to remove heat and products of combustion from a structure on a fire scene — were brought in to assist in venting the gas.
Due to the LEL being high, 2 units of ChemPro100i were brought to the scene.
The HazMat operators used ChemPro100i’s unique trend display feature to track the LEL. With the higher precision of the ChemPro100i the safety of the team was ensured. The ChemPro100i trend rises faster than the meter whole % readings of LEL. This crucial information was used to determine a stay or evacuate decision.
The reading of the trend view also allowed for adjusting the PPV fans if the trend was rising, so the airflow was adjusted to vent the gas. Within 60 minutes the meter was found, and luckily it broke off after the shut off. An old-style boiler valve was shut off and the leak stopped.
ChemPro100i has been in use by the Baltimore County Fire Department since 2007 and the particular units used at this incident were purchased in 2014. ChemPro100i and its trend view function, have been used in several emergency response operations, and proven to be a valuable tool, providing toxic / hazardous gas concentration information, even before alarm triggering levels.
* LEL, short for Lower Explosive Limit, is defined as the lowest concentration (by percentage) of a gas or vapor in air that is capable of producing a flash of fire in presence of an ignition source (arc, flame, heat). Methane concentrations between 5% and 17% will support ignition and are considered highly flammable.
