Heavy snow and ice storms have the potential to compromise natural gas infrastructure in a large area, both aboveground and underground. As a first responder, you must consider the possibility of widespread damage to natural gas infrastructure when sizing up any incident involving a reported natural gas leak, fire and/or explosion during major snow and ice events. Be alert for carbon (CO) monoxide poisoning as well.

Moisture can accumulate in natural gas regulators, relief valves and other equipment and prevent them from functioning properly when it freezes, impeding or interrupting the flow of gas to appliances and furnaces. In some instances, the expanding freezing water can damage the equipment.

Blocked exhaust or combustion air vents

Every year, injuries and deaths result from CO poisoning when exhaust and combustion air vents for natural gas appliances (such as water heaters and dryers) become blocked by snow and ice. CO is formed when natural gas cannot burn completely because there isn’t enough air for combustion to occur. The symptoms of CO poisoning are similar to flu symptoms, including headaches, weakness, confusion, chest tightness, skin redness, dizziness, nausea, sleepiness, heart fluttering or loss of muscle control. If you suspect carbon monoxide, get the victims outside into the open air. Have them breathe deeply and seek medical help for them immediately.

In sustained subfreezing conditions, or during spring freeze and thaw cycles, ice can expand underground and affect susceptible soils, pushing ice and soil upward in an effect called frost heave. Frost heave causes roads to develop humps and dips and can sometimes damage underground natural gas distribution pipelines in the same fashion. Older neighborhoods with older natural gas infrastructure, such as cast-iron mains, are more likely to be affected.

Though natural gas is lighter than air and will always rise whenever possible, gas leaking from damaged underground pipelines can be trapped by ice and snow and migrate some distance before entering buildings, utility vaults or sewer systems. When you are called to a gas leak, fire or explosion, use your natural gas monitor to check around nearby manholes for the presence of migrating leaking gas. Remember, do not open or enter manholes or vaults where natural gas is present until National Grid employees say it is safe to do so.

Though most of these impacts are at the distribution (or neighborhood) level, where smaller pipelines and gas mains are closer to the soil surface, larger transmission pipelines can also be damaged by frost heave. Equipment at metering and pressure-regulating stations is primarily aboveground and is used to remove impurities, such as moisture, and step down pressure from natural gas being delivered through transmission lines. In extreme winter temperatures and storm conditions, this equipment can also be affected by freezing moisture and heavy loads of snow and ice.

In any incident where you suspect or have confirmed that natural gas or carbon monoxide are involved, follow these universal response tactics: