(NewsNation Now) — When it comes to house fires, many people think it’s the blaze itself that kills people. But more often than not, the actual cause of death is smoke inhalation.

Most of the deaths from a fire in a high-rise Bronx apartment that killed at least 17 people and injured multiple others on Sunday were the result of smoke inhalation. This was New York City’s deadliest fire in three decades.

More than five dozen people were injured and 13 were hospitalized because of the blaze, which was started by a malfunctioning space heater.

According to the most recent data from the National Center for Health Statistics, smoke inhalation is the most common cause of death in house fires. In 2019 alone, it accounted for 38 percent of all house fire deaths.

When smoke moves into the lungs, it penetrates the respiratory system’s protective filters, sticking there. What makes this so dangerous are the toxic gases, such as carbon monoxide, which can replace oxygen in the bloodstream.

The primary way smoke inhalation kills is through suffocation from a lack of oxygen. A 21 percent oxygen level is considered normal. At 17 percent, there are impairments, and at 9 percent, people can go unconscious. When the oxygen level is at 6 percent, that is when cardiac arrest or even death can occur.

Children, especially infants, are especially vulnerable in low oxygen situations, as they use their oxygen supply faster than adults.