Gas and Electric Fans

[lilbubs52]

Why are gas fans used for commerical buildings?

I was on a building fire at a school were there was small kitchen fire. The school filled with smoke and 7 gas fans were placed in service in front of two pairs of double doors. Smoke was clear but now the school was filled with CO2. Now the gas fans were shut off and placed three electric fans to clear the CO out of the building. which did the job.

I perfer electric fans over gas. To me using gas fans it is double the work since the CO2 would go right into the building. Some have the extended hose for CO2 but some are placed incorrect that the wind tunnel just takes it into the building.

If using a gas fan use it in a proper way. Gas fans can be use for residential homes in some cases. If use properly then use them otherwise I would stick with electric fans.

[Bones42]

Compare the CFM for equally sized gas fan vs electric fan.

It's been a few years since we have, but the gas fan outperformed the electric fan by a significant margin.

As for the CO theory...if the building was full of smoke...wasn't CO already there? Did you run any actual CO measurements before and after?

We have done some testing and found the actual amount of increased CO was extremely low.

[GTRider245]

CO2 and CO are not the same thing. Just so you know.

We run electric at one department, gas at another. They both have their advantages and disadvantages. All comes down to preference and how you operate.

[fire49]

lil

did someone take readings to confirm levels????

also if ther is a fire already, there are fire gases in the building, and you may add a ppm??

[len1582]

I guess you're referring to exhaust fumes from the fan. In order to minimize them being pushed into the building you need to run the hose from the exhaust outlet away from the fan. It might not eliminate everything completely, but it will help. Along with proper placement.

[ChiefKN]

I guess you're referring to exhaust fumes from the fan. In order to minimize them being pushed into the building you need to run the hose from the exhaust outlet away from the fan. It might not eliminate everything completely, but it will help. Along with proper placement.

Yes, those extension tubes that fit on the exhaust are pretty critical.

With that said, there are some much better electric fans then the old box smoke ejectors of old.

[WD6956]

Compare the CFM for equally sized gas fan vs electric fan.

It's been a few years since we have, but the gas fan outperformed the electric fan by a significant margin.

As for the CO theory...if the building was full of smoke...wasn't CO already there? Did you run any actual CO measurements before and after?

We have done some testing and found the actual amount of increased CO was extremely low.

Well said, i would say the same thing. The CFM of most gas fans far outweighs the possible minor CO issue.

We run SuperVac 16" electric smoke ejectors. We use the P164 which has a claimed 5,200 CFM with the venturi effect as our primary ejector. But we have a pair of Tempest 18" Gas powered fans that push over 15,000 cfm each. A fan that is 2" larger in diamater but is pushing almost THREE times the amount of air is a HUGE improvement. The gas fans are not much larger overall. Only about 3" wider, 5" taller and 8" deeper. And a little less then twice the weight. But no cord to carry, deploy and roll up and no need for generators. And the gas fans have wheels unlike the electric fans. So the additional weight is not really a big deal. And with two people, it's a breeze (excuse the pun).

At the end of the day, i would take a gas fan for commercial, industrial and residential homes any day of the week over electric. The only place i prefer electric fans is for venting apartments where you can put the ejector up in a window.

[FyredUp]

My career FD uses a roughly 10 foot exhaust extension to keep the engine exhaust out of the air flow of the fan.

We also carry an electric PPV fan. Yes folks, they make PPV fans with electric motors now. There cfm is less than a gas powered fan of the same size, but far more than the old negative pressure box vent fans.

[RFD21C]

Another thing that needs to be taken into consideration is the size of the exit opening. If the exit is to small not enough air is going to exit the structure. If you have 7 fans blowing into one building and only one single door open you are not going to remove enough air.

[lilbubs52]

Compare the CFM for equally sized gas fan vs electric fan.

It's been a few years since we have, but the gas fan outperformed the electric fan by a significant margin.

As for the CO theory...if the building was full of smoke...wasn't CO already there? Did you run any actual CO measurements before and after?

We have done some testing and found the actual amount of increased CO was extremely low.

Readings were done cause i did them. The readings i got before the fans was 10 CO2 and when gas fans in service it was on the border of 25 ppm

[lilbubs52]

I guess you're referring to exhaust fumes from the fan. In order to minimize them being pushed into the building you need to run the hose from the exhaust outlet away from the fan. It might not eliminate everything completely, but it will help. Along with proper placement.

To add on to exhaust fumes their was a Tower ladder parked behind the fans that blew the truck exhaust inside.

Yes there was CO2 inside cause of fire but more was added to it. I see the advantages and disadvantages of both my only point to the whole thing is how it was all setup. More work was done that could of been avoided but then again it wasn't my local so nothing i can do. If you saw what i saw you would laugh to see how all setup I do have picture of it but trying figure out how to upload it.

[Bones42]

Readings were done cause i did them. The readings i got before the fans was 10 CO2 and when gas fans in service it was on the border of 25 ppm

25ppm? OSHA allows 35ppm with 8 hours worth of exposure.

25? I'm not even considering that worth mentioning.

[RFD21C]

I bet running the rigs on the bay floor of the firehouse produces higher than 25 PPM CO.

Just so you know it is CO not CO2.

[CKirk922]

Practicality is the name of the game. The gas powered fan is the current best solution to portability.

The electric fan may indeed be equal in cfms but it requires a greater level of strategic positioning and power infrastructure...

One guy can drag (or two guys can carry) a gas fan on wheels and position and run it easily.

It may be akin to dragging an extra hose line trying to drag an electric and heavy power supply cord or lug a generator. Distance may limit the positioning of the fan.

IF you are using this for post attack/knockdown smoke removal- Perhaps,then an apparatus or generator could be repositioned to make fan placement feasible in most situations.

[CKirk922]

I've seen an item in the last year that might have some promise in the construction/remodel industry; There is a door frame ejection fan (electric) that insulation outfits use to negative pressure a home to check for leaks and overall cfm measurement.

This item completely seals the door entry while hanging low or high in the pathway. This might be an excellent niche tool for post fire control smoke ejection but it definitly is not a first line tool.

[GTRider245]

25ppm? OSHA allows 35ppm with 8 hours worth of exposure.

25? I'm not even considering that worth mentioning.

OSHA also says to evacuate a residential dwelling at 10 PPM. This should be the limit for when you stop ventilating, whether it be after a fire or during a leak. Assuming you are ventilating with the sole purpose of CO removal that is.

[fire49]

I've seen an item in the last year that might have some promise in the construction/remodel industry; There is a door frame ejection fan (electric) that insulation outfits use to negative pressure a home to check for leaks and overall cfm measurement.

This item completely seals the door entry while hanging low or high in the pathway. This might be an excellent niche tool for post fire control smoke ejection but it definitly is not a first line tool.

Setup has been around for many years for clean agent room testing even back to halon

They are being seen in residental to calc how much air leakage there is in a building

They do not push much air

[Bones42]

OSHA also says to evacuate a residential dwelling at 10 PPM. This should be the limit for when you stop ventilating, whether it be after a fire or during a leak. Assuming you are ventilating with the sole purpose of CO removal that is.

Min levels of exposure...

OSHA - 50ppm
NIOSH - 35ppm
ACGIH - 25ppm

Here is the link

Here is another interesting link...showing what is occurring and recorded at certain levels....notice that lowest level for US CO alarm is at 30ppm...
http://www.coheadquarters.com/ZerotoMillion1.htm

[GTRider245]

Min levels of exposure...

OSHA - 50ppm
NIOSH - 35ppm
ACGIH - 25ppm

Here is the link

Here is another interesting link...showing what is occurring and recorded at certain levels....notice that lowest level for US CO alarm is at 30ppm...
http://www.coheadquarters.com/ZerotoMillion1.htm

Also notice the "action level" for public safety is 9PPM.

[Miller337]

I bet running the rigs on the bay floor of the firehouse produces higher than 25 PPM CO.

Just so you know it is CO not CO2.

Oh yeah, It really peeves off the gas moniter on the SCBA compressor.