Window A/C units - Eastchester Working Fire

[hudson144 150]

Recently read about a member of Eastchester NY Fire Dept. getting hurt this AM from a falling A/C unit. I hope he is ok. Being that we are in the summer season the above mentioned incident can be a reminder of the hazards that we may face. Many window mounted units are not properly installed in the window. I am sure that many of us on here have at one point or another just put the window unit in and shut the upper half of the window holding it in place. Fires above the ground floor may be a hazard because of the window units. I am not sure what the weight of a 5000 BTU unit is but just imagine the damage that a unit can do if it fell out of the 2nd floor and above windows. Even if a unit is mounted in with the proper mounting brackets the hazard is still present because if you have a fire condition that generates enough heat to melt or burn away the vinyl window the window may fail and the window A/C unit can fall below. This condition may still be present throughout the year because many units are not removed after the summer months and are still in the window for 12 months. Be safe and look for theses hazards

* A 5000 BTU UNIT WEIGHS APPROX 43 LBS,USUALLY THE SMALLER UNIT THAT IS COMMONLY USED!

Edited July 1, 2008 by TR54

[DonMoose 3]

LoHud Report

Dangerous situation - just wondering what can be done to avoid this in the future.

[Oswegowind 17]

Look up, don't stand below it.

[PCFD ENG58 1,085]

Can some smart guy out there find out @ 10 ft x 43 lbs. how fast is it traveling per floor when the mounts fail ?

[Oswegowind 17]

9.8m/s squared... I know there is a formula involving this info, m+dx9.8ms=x, x is force I think...boy it has been a long time since physics!

[Guest emtb23]

Can some smart guy out there find out @ 10 ft x 43 lbs. how fast is it traveling per floor when the mounts fail ?

The weight isn't important. Neglecting air friction, buoyancy, etc., anything that falls from 10' will hit the ground at 8.1 m/s.

[SRS131EMTFF 471]

http://en.wikipedia.org/wiki/Terminal_velocity

this article from wikipedia on terminal velocity says that "An object falling on Earth will fall 9.81 meters per second faster every second (9.81 m/s²)."

So in our situation, the AC unit will reach terminal velocity in about 32.2 feet.

However, in a ten foot fall, according to my calculation, the force of the AC unit hitting the ground would be tripled to more than 120 pounds

but i believe that my assertions and assumptions could be wrong

Edited July 1, 2008 by bvfdjc316

[Oswegowind 17]

Ok, here goes...went to a physics site!

Velocity of falling object, aka impact velocity:

v=square root of (2xgxh) in this case the velocity = the square root of 2 times 9.8m/s sqd times the height (in meters). Hence, the impact velocity in this event is 5.62164417.

How did I get there? 10 feet = 3.048 meters (1 foot is .3048 m), 9.8x3.048 got me 3.22, when squared, I get 10.3684 and when multiplied by the original height of the object 3.048m, I got 31.6028832 and typed "square root of 31.6028832" into the google tool bar and it gave me the answer...(just found out the google tool bar is also a calculator).

Next...

Physical Energy of the falling object:

PE=mgh in this part the physical energy is equal to mass times gravity (9.8ms2) times height. 43 lbs is 19.55 kg (1kg = 2.2lbs...) the height is 3.048m and the gravity is 3.22m/s2

The PE is 617 or so kg.

Kinetic Energy of the falling object:

KE=1/2 mv sqd

KE = 1/2 19.55kg times 5.62164417 sqd.

KE = 308.91818328

How does this translate to common english? I don't know. However, I have personally seen an incident like this a few years back on Cliff St in Yonkers...some may remember. It was a 6 year old child, A/C fell on him from 3rd floor window, approx 18-20 feet. Child had bi-lateral pneumo and posturing was evident u/a. Not a great sight! However, the child turned out okay, and walked out of the Med Ctr a month later. Hopefully, the Eastchester FF will have great results too.

And my final result is that it would feel as if a 280lb gorilla landed on him without explanation.

Edited July 1, 2008 by Oswegowind

[VFD L29 0]

I just took a physics test so this stuff is fresh in my mind. I used an equation that looks like this.

final velocity squared = inital velocity squared + two times the acceleration (9.81 m/s2) times the distance.

and i got 17.3 mph

[firecapt32 282]

do all the calculations you want it had to hurt. I understand everyone is ok becarefull out there.

[SRS131EMTFF 471]

What we need is the amount of force that an AC unit will create when dropped from a height of 10 feet. We have a 43 pounds AC unit will drop at a "constant" rate of 17.3 MPH hitting the ground with x force.

the equation is mass times distance or rate = force

so, 17.3mph x 43lb= 743.9 lb

again this is what I can calculate given my limited knowledge of physics and my math skill skills.

Edited July 1, 2008 by bvfdjc316

[Guest]

I know this is totally diverting from the original topic, but I figure that since I just took the AP Physics (Mechanics C) exam, i'll chime in. Its all about the PE or potential energy, which is converted to Kinetic Energy and is the total amount of energy transferred in the impact. For one story, this would be 19kg times about 3 Meters times gravity, so about 570 j. Converting to a unit that means something to many members here, that's about 420 lb. ft. of force. None of that matters though, be careful of falling window units, they will ruin your day. I wish him a speedy recovery.

[Guest alsfirefighter]

I was taught once that Force= Mass x Velocity (squared). That is also what the state uses in the EVOC curriculum when discussing the train vs fire apparatus collision in Culpepper, VA. The mass alone sounds worse enough.

I hope the brother from Eastchester is ok.

Remember to look for these with your intial size up and if you are assigned to the exterior laddering and such push them in. I once came off a roof to find a firefighter in my department trying to pull one out with a pike pole while standing underneath it!

[Bnechis 3,961]

Since the time to do the math is longer than the time for the AC unit to hit the ground (or anyone in its path). Your only hope is that someone (including you) did a proper and continues to do a proper size-up and stays out of its path.

[KBR359 11]

Just wondering, since this was a Working Fire with 4 Engines, Ladder 16, and Tower Ladder 17, was the Eastchester Fire Dept. SAFETY OFFICER on the scene when this incident occurred? Also, I hope that the TWO Brother Firefighters who were injured at this call are doing OK tonight. Great stop Gr # 4 and Capt Lou.

[DonMoose 3]

Look up, don't stand below it.

Not exactly what I meant. In terms of window/air conditioner design is there anything that could be done to prevent this? Metal window frames? Different brackets, etc.

[e92l44 0]

What can be done?

Work from a ladder or platform and push the A/C inside the window and inside the structure.

If you worry a firefighter may be under it, bang on it a couple of times, yell in the window, whatever you can to warn them, and slowly push it in.

[FirNaTine 370]

I once came off a roof to find a firefighter in my department trying to pull one out with a pike pole while standing underneath it!

That's probably because he was usually assigned to the Engine Co. and only had one job to perform like the FDNY guys.

[Guest alsfirefighter]

LOL. Good one Fir. ..good one brother...lol. I can't comment any further on status or "assignment," I don't have a note from my mother.

Didn't know till now..but I hope the brothers are all ok.

[hudson144 150]

ok what do you do if you are inside the room,1 window with the A/C properly mounted and you are assigned to vent the room-worse yet you gotta get out through that window. Tools of choice,communication to your officer, etc.

[191SH 4]

in my building (68 units) i mount all ac units and screw them into the window frame. i dont think it matters on the velocity, the point is to watch above , below and around you at all times because unless you installed it, fixed it, or replaced you dont know how strong or sturdy it is.

stay safe all

[ny10570 745]

donmoose, if people installed them the right way there would be no issues. But with anything build it idiot proof and they'll just build a better idiot.

As far as removing an AC unit, on the inside pull it in. They are all suppose to be installed and removed from the inside so thats going to be the easiest way 9 times out of 10. Even that large in the wall units are usually only held in with a few screws and cheesy stamped metal frame. Easily overcome by someone who takes a second to find the spots that are holding.

[ajsbear 11]

I remember year ago getting hit with an AC unit that was mounted about the door to a store. It only dropped a few feet and dented the old leather. That hurt. I saw double for a while.

(no comments that that explains a few things)

Edited July 2, 2008 by ajsbear