I hope to direct this question to fire fighters or other experts in the field. My home has a networked fire alarm that activates all of the alarms if one detects smoke. It is also tied in to my home automation system so that I can get alerts, etc. My home also has a large poweful whole house fan. I don’t know the rating, but it gets the house aired out pretty quickly. I have seen house fires in the past where the fire fighters put large fans in the window - presumably to get the smoke out as quickly as possible. My question is therefore does it make sense to automate my house fan to turn on when the fire alarm activates, or would this be a bad idea and potentially make the fire worse? Any expert thoughts on this are appreciated.
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My guess is that it’s going to turn your house into a chimney and feed the fire.
Usually in industrial fire systems, the system is set up to cut off HVAC or other air systems in order to contain the fire. Leaving them running increases the risk of feeding the fire or transporting hot ashes or cinders through the building, making things worse for the building and any occupants who haven’t evacuated yet.
NICET certified fire alarm tech for 20 years here… HVAC shut down is done in coordination with dampers not to contain the fire, but to prevent moving smoke through the buildings. smoke is the killer, not so much fire.
stairwell pressurization fans force fresh air into stairwells to provide egress routes with breathable air.
AFAIK there’s no design consideration to attempt to smother a fire
I never knew about the stairwells, that’s cool.
Just want to clarify I’m not a fire alarm guy, although I do work alongside them and have picked up some stuff. Buildings are neat.
25 years as a volunteer firefighter, almost half as an officer / Chief.
Don’t do it.
When the fire department puts a fan in the door, or opens windows, or cuts a hole in the roof it’s for specific reasons, and there’s one thing in common on all of them: the fire department is on scene!
If we’re putting a fan in the door it’s either to exhaust the smoke after the fire has been extinguished, or it’s to try and clear smoke while the attack team is putting the fire out. The latter is an advanced technique that isn’t practised by all departments, because if the fire isn’t out you’re giving it air and making it bigger.
Cutting holes in the roof is normally done to try and get the smoke out while we’re putting the fire out. The location of the hole is important and the fire will move towards the hole, as someone mentioned “the chimney effect”. We only cut the hole when there’s water on the fire, or it’s ready to be. Again, it will make the fire grow so we have to be in a position to deal with it. Removing the smoke cuts down on the chance of a flashover or a smoke explosion (“backdraft”).
When the fire alarm goes off in commercial buildings it should be cutting the HVAC so that It doesn’t move toxic smoke through the building. (a) it will kill the occupants, and (b) it then makes it more difficult to find the source.
If your whole-house fan isn’t on when your smoke detectors activate then leave it off. If it is on, and you can tie it into your smoke detectors, then it would be a good idea to turn it off. If the fire department get there and it’s something dumb like someone burned the toast or, even worse, the bacon!, and there’s a light haze through the house then you can tell the incident commander that you have a whole house fan and can turn that on to get the smoke out.
If you’re reading this and you don’t have a whole-house fan, and you do something dumb like burning toast, or bacon, or another culinary mishap (current jargon for “burned food”), don’t feel bad about calling for the fire department. It happens every day, we’re only too happy to come and do it, we have the tools and the training for it. It;s not really dumb, but it’s still dumb.
You should do the opposite. A large amount airflow will give more oxygen and airflow to fire and will possibly allow embers to spread. In commercial buildings, the fire alarm is often tied to shutting off the HVAC upon an activations.
Besides that, one of the first things firefighters will do upon arriving on scene of a structure fire is turn off the electricity and gas to the home. So, all you fancy automation will mean nothing and they will still probably cut a hole in your roof.
smoke is what kills you in a fire, so getting the smoke out of the house as soon as possible is a good idea.
any risk of “feeding the fire” is operating under the assumption that all the oxygen has burned out of the space, so the occupants are already dead at that point.
if you want to turn on your fan, you also need to provide a means for fresh air to enter the building, or you’re just going to create negative pressure in the structure and not end up moving much air.
if you can automate a window opening as well, i don’t see any problems with running the house fan.
any risk of “feeding the fire” is operating under the assumption that all the oxygen has burned out of the space, so the occupants are already dead at that point.
Not completely true, wind will (airflow from a whole house fan) spread fire. There is a reason fire danger is increased as wind speed goes up. It allows heat to spread horizontally instead of vertically which leads to combustion of surrounding materials. It leads to bigger fires more quickly.
Not a firefighter, but seem like you would be feeding fresh air to the fire.
Will help pull out the smoke but will definitely feed the fire (creating more smoke). Bad idea
This is along the lines of what I was thinking as well. It may accelerate the fire, but the alarms are already activated, so in theory we are getting out of the house. Getting the smoke out makes that easier? Hoping for more answers as it seems both sides of this have merit so far.