Gas furnace backfires or explosions generally occur when the furnace misses ignition.
A small explosion occurs when fumes build up because the ignitor delays lighting up.
When the thermostat signals for heat from the furnace, it prompts the gas valve to open, sending gas to the burners. Modern gas furnaces are ignited by the ignitor, while pilot lights ignite the older systems. The burner flames from the combustion after ignition heat the HVAC unit’s heat exchanger. The HVAC equipment’s blower pushes the heat produced in the combustion process throughout your home. So when there is an ignitor or sensor delay due to a weak or dirty pilot light, your gas furnace backfires or causes a small explosion. When too much primary air mixes with gas, your gas furnace won’t light quickly, causing gas build-up. Likewise, too little gas at the burners makes it hard for the gas-air mixture to light up. Call an HVAC technician to fix this problem. When debris builds up in the furnace, it leads to an explosion of the atomized oil. These explosions are a result of faulty valves, a dirty filter, or a bad oil burner. It is crucial to keep the area around the furnace clear of clutter and debris. Do not place gasoline or paint thinners in the same room as the furnace. These could cause a big explosion. It would help if you replaced your HVAC air filters regularly to prevent furnace backfires. Check your HVAC equipment for expanding air ducts which could cause loud bang noises. Typically, expanding air ducts make noise due to a lot of static pressure in the ductwork. Too much static pressure pushing on your ductwork will cause it to expand and cause a banging noise. Static pressure is brought about by undersized ducts, closed supply vents, and dirty air filters. Regular maintenance will help eliminate cases of gas furnace backfires.