How a Home Fire Spreads

Ignition can occur when cooking oils reach 600 degrees, but a burner set on high can easily reach 1,000 degrees.

  • In the first 30 seconds, fire can spread via oily spatters and coatings on utensils and surfaces and set afire flammable items like food packaging, paper towels or tea towels, for example. Already, smoke is an issue as it may contain toxic gases.
  • Within the first minute, as more flammable items ignite and the fire spreads, a mix of hot gases and smoke will rise and expand. The gases typically contain poisonous chemicals like carbon monoxide and hydrogen cyanide.
  • Within two minutes, heat from the fire will radiate temperatures of 190 degrees to surrounding areas. Meanwhile, the mix of gas and smoke will increase and begin expanding and rising up into other areas of the home.
  • By three minutes, the upper layers of gases can reach temperatures of 400 degrees or more. As the fire burns, it heats building components and furnishings, releasing additional toxins like arsenic, lead, ammonia, hydrogen chloride and isocyanates. Temperatures become intense enough to cause objects to auto-ignite.
  • By three-and-a-half minutes, temperatures can reach 1,100 degrees, and flashover can occur. As everything bursts into flames, the fire consumes oxygen and may “roll” or flare in search of more fuel. Flashover and the increase of flame may escalate temperatures to 1,400 degrees.
  • Within four minutes, as it spreads to other rooms, the fire repeats the process to heat not only a room’s contents but also building components. As fire penetrates walls, floors and ceilings, it can travel via the home’s structural framework and systems.
  • By five minutes, flashovers and auto-ignition can occur throughout the home. Temperatures reached thereafter may be sufficient to melt steel plates and collapse floors and roofs. Total structural collapse can result within six minutes of a house fire’s initial ignition.

Fire is more than flame. It brings with it sustained extremes of intense temperatures, rapidly shifting pressures, poisonous vapor and smoke damage, and both visible destruction and less apparent compromise.

Dangers of a Home Fire

The takeaway is that fire touches everything even if the actual flames did not. So, even a limited ignition can present health hazards and have the potential to compromise a home’s structural integrity as well as its mechanical and electrical systems. A home touched by fire can be a dangerous place in ways that are not immediately obvious.

  • Glass from windows and home décor often shatter. Broken glass may be not only sharp and in unexpected places but also coated in chemicals released during the fire.
  • Embers may linger in compartmentalized void spaces—inside walls, beneath floors or in ceilings, for example—only to resume burning later.
  • Building components and structural features may appear relatively undamaged but be severely weakened by thermal stress.
  • Electrical and mechanical home systems may be damaged and may no longer be safe or fully functional.
  • Utility hookups may no longer be safe or secure.
  • Smoke damage and accompanying chemical-laden gases can permeate furnishings and areas of a home otherwise untouched by flames.
  • Materials affected by heat will continue to off-gas toxins long after flames are extinguished.

In addition, fire departments often open walls or even roofs to help slow a fire and disperse smoke and fumes. Even extinguished areas may suffer extensive water damage and mold or be contaminated by toxic chemicals and precipitate.