Electrical arcing can ignite insulation, leaking natural gas, methane from decaying organic matter, fumes from smouldering insulation,[15] or even gasoline poured down the toilet.[16] This can cause a fire, power outages, and in some cases, an explosion.[15] In the United States, they are most common in New York City, with 3,369 manhole events, including 32 explosions recorded in 2014.[17] They were most common in summer due to increased electricity use. Chicago reported fewer than 10 events with no explosions, despite also using road salt in the winter.[17]
