BY BRIAN CRIMMINS AND ALIDER PRATTS
The primary concern at any gas emergency is the likelihood of an explosion. Accumulated explosive gas can be deadly if it reaches an ignition source, even when firefighters are far away. According to John Norman’s Fire Officer’s Handbook of Tactics (fourth ed.), gas explosions can create far greater forces, collapsing walls and even entire buildings, sending debris great distances. Gas emergencies can be deadly and destructive for civilians and firefighters alike.
Gas emergencies present a unique threat to the safety of firefighters. In the metropolitan New York area, several devastating gas explosions have occurred recently, such as in New York City’s East Village (2015); Paterson, New Jersey (2016); Trenton, New Jersey (2016); and the fatal 2016 Bronx, New York, explosion that killed Fire Department of New York Deputy Chief Michael J. Fahy. Many more gas explosions have been documented in the New York metropolitan area and throughout the United States.
(1) A controlled perimeter keeps vehicles, pedestrians, and staged responders away from hazard areas. (Photo by Dan Martland.)
Safety
Safety at gas emergencies depends on using the proper tools and techniques. To ensure the highest level of safety, it is critical that responders follow 10 life-safety tactics at gas emergencies:
1. Preplan your response area. Since there are different types of combustible and explosive gases, it is critical to know whether your response area uses natural gas or propane. These two gases have different properties and require different detection tools and techniques.
With a vapor density of about 0.60, natural gas is lighter than air. Under normal conditions, natural gas will rise to the ceiling of a room or release into the atmosphere. To measure natural gas, firefighters use single gas, multigas, or flame ionization detectors. Readings are typically recorded as parts per million or as a percentage of the lower explosive limit (LEL). It’s important to note that some detectors that measure natural gas alone are ineffective tools for measuring propane gas.
In contrast to natural gas, propane is heavier than air. Propane will sink to the floor; collect in basements, sewers, and other low areas; and then migrate until vented or ignited. Firefighters typically use a photo-ionization detector (PID) or a multigas meter with a PID sensor to measure propane. Readings are typically displayed as volatile organic compounds. PID sensors alone are typically ineffective tools for measuring natural gas.
Firefighters must be familiar with their response area to understand the hazards present at a gas emergency. Although methane (the primary component of natural gas) and propane are both explosive gases, they have drastically different properties and require different response procedures. Industrial and commercial occupancies in a response area may present additional challenges if other explosive gases are released. Preplanning, material safety data sheets (MSDSs), contact with the Chemical Transportation Emergency Center (CHEMTREC®), and collaboration with industry and utility experts will further mitigate hazards to firefighters.
As a precaution, fire departments should have ongoing communication with utility companies to monitor any ongoing repairs to damaged underground gas supply lines. Construction and changes in population may impact the demand on underground utilities. Underground gas leaks can be especially deadly if gas migrates into different buildings.
2. Calibrate and maintain gas detectors. Gas detectors are reliable only when they are properly maintained and calibrated. Firefighters can be rough with equipment and cause unintentional damage. For example, members may inadvertently drop gas detectors; allow them to get wet; or excessively expose them to dirt, dust, or hazardous chemicals. These actions can cause damage that leads to unreliable readings.
To ensure reliable readings, firefighters must perform periodic bump tests and calibration in accordance with Occupational Safety and Health Administration (OSHA) regulations and manufacturer specifications. Bump testing involves exposing a gas detector to a target gas. If the alarm sounds, then you know that the detector is working and is not clogged by dirt, water, or debris. Calibration is a distinct process that ensures a detector’s accuracy. It involves measuring a gas detector’s ability to read a target gas and display accurate readings. Always follow the detector manufacturer’s specifications for bump testing and calibration.
3. Never trust your nose alone. Methane, the principal component of natural gas, is odorless and colorless. Utility companies add the odorant mercaptan to help people identify natural gas leaks through its distinctive smell. Propane is also odorless and supplemented with the ethyl mercaptan for odor. Unfortunately, odorants can be filtered out of gases when they travel long distances, travel in pipelines, or migrate underground. Underground gas leaks may therefore be difficult or impossible to detect without gas meters. Always use the appropriate gas detectors, and never rely on your sense of smell alone at a gas emergency.
4. Always use at least two gas detectors. Using several gas detectors simultaneously minimizes the chance of failure in detection. Detectors are complicated instruments that if misused may provide inaccurate readings. As mentioned above, exposure to dust, dirt, water, or hazardous materials can result in an inaccurate gas reading. Other factors that can skew results include dropping the detector, failing to properly calibrate it, cleaning/decontaminating it with bleach or other chemicals, and not collecting a baseline fresh air sample to “zero out” the detector.
Given the wide range of possible erroneous readings, obtaining readings using at least two detectors concurrently is a sensible way to avoid possible false readings. When two detectors show drastically different readings, this indicates that the equipment must be placed out of service for recalibration. Firefighters should then use different detectors to analyze the atmosphere
5. Control the perimeter. We commonly see fire apparatus, police cars, and other vehicles parked at the front door of a reported gas emergency, a dangerous and unacceptable practice. If an explosive atmosphere is present, then one of these vehicles may supply the ignition source needed for an explosion. Also, vehicle exhaust may accidentally enter the building and fill it with toxic carbon monoxide and other fumes, which will skew gas detector readings. To avoid these hazards, personnel responding to a gas emergency must establish a safety perimeter.
Officers should request the gas utility company to respond and inquire about construction in the area. Stage apparatus a safe distance from the reported address, and exclude all vehicles and pedestrians from the safety perimeter. At suspected pipeline leaks, review the 2016 Emergency Response Guide precautions and establish a perimeter of at least 330 feet.
At an incident where both natural gas and propane are present, remember that propane is heavier than air. In this case, respond to gas emergencies from upwind and uphill. Keep vehicles away from areas where gas can collect underground; and never park above storm drains, catch basins, manholes, and sewer vents. Do not use road flares in the area.
6. Limit the number of personnel in the hazard areas. After calling for the utility company and establishing a safe perimeter, determine whether emergency personnel need to enter the hazard area. When low levels of gas are present, firefighters should investigate the area and isolate the problem. Personnel can easily mitigate most gas emergencies by relighting a pilot light or closing a valve on a stove that was accidentally opened.
If there is no immediate solution, firefighters must continue their investigation while constantly monitoring for gas levels and practicing safe tactics. Only a minimum number of responders should be allowed near the hazard area, and they must wear firefighting personal protective equipment (PPE) and self-contained breathing apparatus (SCBA). Stage all other personnel in a safe area.
(2) Always investigate any road repairs as a possible cause of gas emergencies. (Photo by Alider Pratts.)
7. Control ignition sources. Controlling ignition sources is one way to avoid an explosion when explosive levels of gas may be present. On arrival at a reported gas emergency, do not ring doorbells or turn on light switches. Beware of static electric shocks from clothing or carpets. Disallow smoking and cell phone use. Turn on flashlights prior to entering the area in question. Use only intrinsically safe radios and equipment that will not generate sparks. Finally, avoid forcible entry tactics that involve striking steel tools together.
8. Use proper sampling techniques. Proper gas sampling begins with fresh air readings (also called “fresh air calibration” and “zeroing out” the gas detector). This is important because residual gas may be trapped inside the gas detector from the last time it was used. Fresh air samples also provide a baseline for future readings. Always obtain the fresh air sample in fresh air, away from sources of vehicle exhaust or other contaminants that will result in misleading or false readings.
After having taken the fresh air sample, begin detection from outside the hazard area to ensure that you do not unknowingly walk into an explosive environment. Move slowly throughout the entire building to give the detector time to sample the air and display results. Take readings near gas meters, relief valves, gas pipes, fittings, furnaces, and appliances. Sample air from basements, utility closets, laundry rooms, and cooking areas. Check high and low areas to gather complete information. Use probes to check behind locked doors and in confined spaces. Take readings in manholes, sewers, and adjacent buildings to detect gas that may be migrating underground. Apply soapy water around gas fittings and connectors to check for bubbles that indicate a leak. Immediately isolate faulty appliances by closing the gas shut-off valve.
If the source of a gas leak is unclear, interview occupants for more information. Has there been any construction in the area recently? Have any previous gas leaks been fixed recently? If occupants report feeling ill, be sure to administer first aid and request emergency medical services response.
(3) Gas emergencies may require multiagency response with fire departments, utility companies, police, and emergency medical services working together. (Photo by Dan Martland.)
Ventilation is an important aspect of gas sampling. Provide natural ventilation by opening doors and windows, or supply positive pressure ventilation by placing a large fan directed into the building’s entry. Never use a negative pressure ventilation fan to pull exhaust out of a structure because it creates an ignition source. After you have isolated the problem, close all windows to see if gas accumulates again. More than one gas leak may be present, or you may not have isolated the problem.
9. Take precautions when your detector reads 10 percent of the LEL. When gas detectors display 10 percent or more of the LEL, take serious precautions, including the following:
- Confirm that all members are in full PPE with SCBA.
- Request more personnel to the scene; stage members in flanking positions, a safe distance away from hazard areas.
- Establish a primary and secondary water supply.
- Stretch a hoseline as a precaution.
- Evacuate the building and adjacent buildings.
- Shut off gas at the meter and secure it with lockout/tagout procedures.
- Notify the utility company to expedite its response.
- Ventilate the building.
- Relocate the command post to a safe area upwind and uphill.
- Decentralize command by assigning safety and accountability officers and group and division supervisors.
Never wait until gas reaches 100 percent of the LEL before taking precautions for three major reasons:
(1) Although your detector may display less than 100-percent LEL, gas may have accumulated up to the explosive range elsewhere in the building. Firefighters and residents may already be in the path of a possible explosion.
(2) Your detector may not show accurate readings because it has not been calibrated or because someone failed to calculate the appropriate response factor.
(3) Precautions take time. With readings at 10 percent LEL, there is clearly a major problem. Begin preparing for a potential explosion early.
10. When appropriate, rely on the experts. Firefighters customarily have four main responsibilities at a reported gas emergency:
(1) Determine if there is a problem.
(2) Prevent an explosion.
(3) Isolate the problem.
(4) Call the experts.
It’s important for firefighters to isolate rather than attempt to correct a gas leak. Although firefighters have tremendous skill sets and can be amazingly resourceful, they should never attempt repairs to stop a gas leak. Incorrect repairs will only add to the problem. Instead, shut off gas to a defective appliance and instruct the owner to call for immediate repair. If necessary, shut off gas at the meter. Do not attempt to modify a furnace, hot water heater, or stove. Do not open manholes or tamper with underground gas controls. Even if a firefighter is a licensed plumber, that person is responding as a firefighter and should call the experts.
These 10 lifesaving tactics will help to ensure a safe and effective response. Gas emergencies may be quick and routine or may develop into large-scale operations. The fire department response must, therefore, be scalable to address all hazards present and ensure firefighter and civilian safety. Training is critical for firefighters to know their equipment and their responsibilities. Above all, members must remember the three universal priorities of life safety, incident stabilization, and property conservation.
BRIAN CRIMMINS is a battalion chief and tour commander with the Hoboken (NJ) Fire Department. He has a BA from Boston College and an MPA from John Jay College.
ALIDER PRATTS is a battalion chief with North Hudson (NJ) Regional Fire and Rescue. He is a NJ State-certified fire instructor and teaches at the Monmouth County Fire Academy.
