Though the possibility of a fire breaking out in your home is small, a few basic safety measures can make all the difference in saving lives, says one retired state fire marshal. 

"People always believe it won’t happen to them," Bill Kramer, a retired New Jersey state fire marshal, told Fox News after a fire filled a high-rise Bronx apartment with smoke, killing 17 people – including eight children. "You should always be thinking about the what-ifs," Kramer said.  

Residents trapped inside the apartment building pleading for help.

Residents trapped inside the apartment building pleading for help.  (Reuters Photos)

FDNY Fire Commissioner Daniel Nigro said preliminary evidence suggests the fire "started in a malfunctioning electric space heater" in an apartment unit spanning the second and third floors of the 19-story building. The door to that apartment and another door to a stairwell was left open, allowing smoke to spread throughout the whole building, he said. 

Initial reports indicated 19 people were killed in the fire. Authorities later modified the death toll to indicate 17 people – eight children and nine adults – had died. 

"People always believe it won’t happen to them…You should always be thinking about the what-ifs"

FDNY-Uniformed Firefighters and the Fire Officers' association officials doubled down on the belief that the fire was caused by a space heater malfunction. They also revealed Monday there were no sprinklers in the building. A source familiar with the matter told Fox News Digital the structure was built in the 1970s, when building code requirements were different.

Current city code calls for buildings to have self-closing doors, a system that would have stymied the blaze and resulting smoke, officials said. But the structure was built using federal funding and therefore followed a different code from that of the city, FDNY and fire organization officials said. 

"So, a lot of the safety features we have in the other buildings in New York, New York City aren't in these buildings, but there are some safety factors," FDNY-Fire Officers Association President Lt. James McCarthy said Monday. "With federal funding for the building, they don't necessarily have to follow … New York City fire code."

Property records obtained by Fox News Digital link the building to a man named Rick Gropper, who was a contributing member of the transition team on housing for newly minted Mayor Eric Adams, according to local reports.   

Speaking to Fox News on Sunday, Kramer, who was with the New Jersey Division of Fire Safety for 34 years, said it is imperative that doors remain closed in the case of a fire, so that smoke does not contaminate other parts of the building. Making sure that you close doors behind you when evacuating will keep smoke from traveling throughout the building, stressed Kramer.

PHOTOS: HORRIFYING PICTURES PAINT DEADLY NYC APARTMENT FIRE AFTERMATH

In this photo from the UL Firefighter Safety Research Institute you can see the importance of sleeping with your bedrooms closed at night.

In this photo from the UL Firefighter Safety Research Institute you can see the importance of sleeping with your bedrooms closed at night.  (UL Firefighter Safety Research Institute)

By just closing your door and creating a barrier to a fire's progress it gives you precious time to use your practiced home fire escape plan.

By just closing your door and creating a barrier to a fire's progress it gives you precious time to use your practiced home fire escape plan. (UL Firefighter Safety Research Institute)

In a multiple-story building like a high-rise, if you do find yourself in a situation where there is smoke, don’t panic, but don’t go, Kramer said.  If you can’t get out of your unit because the hallway is full of smoke, or the stairway is full of smoke, return to your unit and call 911 to let them know where you are, he said.

"Heat rises, so (the smoke) is going to go all the way up to the top of the stairwell, and it’s going to start banking its way down," Kramer said. "Any doors that are open from the stairwell into other hallways are also going to contaminate those hallways as well. So, anybody above the fire is in danger." 

He stressed that if you live in a one- or two-family dwelling, the single most important thing a person can do to protect themselves in the event of a fire is to keep smoke alarms working and change the battery on a regular basis. 

FDNY at the scene of a data fire at an apartment building in the Bronx.

FDNY at the scene of a data fire at an apartment building in the Bronx.  (Getty Images)

If a fire breaks out, Kramer said it is important to immediately exit, pull the fire alarm, and notify everyone else in the building. The next step would be to exit through the stairwell. But if each stairwell is filled with smoke, residents should remain in their apartment and notify 911 of their location. 

HOUSTON FIRE IN HOME WITH NO SMOKE ALARMS LEAVES 1 DEAD, 3 HOSPITALIZED

Approximately 200 firefighters responded to the Bronx apartment fire on East 181st Street around 11 a.m. Sunday. Four of them were injured, including one seriously, though none of the injuries were life-threatening, fire sources said. 

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Sunday’s blaze comes less than a week after a Philadelphia fire killed 12 people, including eight children.

Fox News' Jeremy Copas contributed to this report.