While the odds of getting struck by an exploding manhole cover are low, they’re not zero. According to the 2021 New York City Mayor Management Report, the New York Fire Department responded to 261 instances of manhole covers being dislodged by the force of explosion in the 2021 fiscal year. This is not a problem unique to New York; manhole covers explode all across the country. Chicago has received over 3,500 complaints of missing manhole covers and grates since 2016. A manhole cover explosion was recently caught on camera in Boston. And one manhole cover explosion even recently destroyed a car in Miami.
So what do you do to make sure an exploding manhole cover doesn’t come your way? By being on the lookout for a few telltale signs, you’ll be able to identify a manhole cover explosion before it happens and alert those who have the capability to prevent it.
What makes a manhole cover explode?
Exploding manhole covers mostly happen during the winter months, though it is possible for them to explode year-round. According to New York City’s electric, gas, and steam supplier Con Edison, it all starts when the salt used for snow removal mixes with water and drains down the manhole. Next the salt water, which conducts electricity, will submerge the electric cables and generate heat by eroding the insulation layer of the cable, making contact with the live wire. This will then create gas and smoke as the insulation burns, which will lead to conditions where a spark can form from the wires, igniting the built up gas.
The resulting explosion can cause the manhole to be lifted as high as 50 feet off of the ground, becoming an extremely dangerous projectile for anyone in the area. If you’re looking for an in-depth animation of this process from start to finish, the Weather Channel has got you covered.
How to spot an imminent explosion (and what to do if you see it)
The circumstances that lead to a manhole cover explosion slowly build over time. If you ever see smoke coming from a manhole, you should immediately step away and call the emergency services to deploy the fire department. Con Edison spokesperson Sidney Alvarez told Bklyner, “I know [people] whip out the phone and take video. If they can first call 911 or us and then take video, that would be better. The sooner they call us, the sooner we can get out there and make it safe.”
If you’re unsure if the gas you’re seeing escape from the manhole is smoke or just steam, it’s still recommended you report it, as unaddressed leaks from steam systems can also endanger public safety. If you see a missing manhole cover on a street or highway, no need to call 911, but instead report it to local authorities. Additionally, Con Edison also recommends that you keep pets away from lampposts, grates, and manhole covers during “post-storm” periods.