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May 3, 2006 6:25 AM   Subscribe

Prompted by this mention of a 10-alarm fire, where the hell did that scale/terminology come from, and how does it work?

You hear in the news fires described by their varying levels of "alarm" status. The best information I can gleam is that's how many firehouses are required to bring the fire under control? Does the chief or some such determine how many "alarms" must go out, if this is the case?

What's the largest "alarm" fire, say, in the US, to date? (Exclude WTC, because as the article mentions, it was obviously way up there on the list.)

Also, does the scale apply to wildfires as well, or are they on a different scale? (I always hear about them in terms of containment and acres burned...)

If you're able to Google or Wiki this, let me know your search terms, since the only thing to provide even the most remote results is one-alarm two-alarm in the same query.
posted by disillusioned to Grab Bag (10 answers total)
I've always understood it to mean the number of firefighting crews involved. A five alarm fire would require crews from five different firehouses. Thus, 5 seperate alarms would need to be sounded.
posted by cosmicbandito at 6:36 AM on May 3, 2006

I'm curious to know the official answer to this as well. I always figured it was as cosmicbandito just noted, but the New York Times piece on this fire said "70 units" fought this fire and not 10. So how's a unit different from an alarm?
posted by werty at 6:38 AM on May 3, 2006

Here's the same question at Google Answers. The answer there is pretty much what cosmicbandito said.
posted by aiko at 6:42 AM on May 3, 2006

werty: I assume a unit refers to the number of fire trucks, ambulances, and fire chief cars that go to a scene. Each firehouse can have any number of different (and different types) of fire trucks.

In terms of "who" decides, the units on the scene/commander, will decide if they need to call for help from more firehouses. Some types of fires, like in apartment buildings and so on, are almost automatic multiple alarm fires to avoid runaway fires, I believe.
posted by skynxnex at 6:45 AM on May 3, 2006

"70 units" fought this fire and not 10

Each firehouse can (and often does) contain more than one unit, i.e. Ladder 10, Rescue 400, etc.
posted by ChasFile at 6:48 AM on May 3, 2006

Another thing to keep in mind is that an "alarm" in today's fire departments mean something different in terms of number of firefighters than it did years ago. Most fire departments are running with fewer firefighters per vehicle (partly because of cost and partly because, on average, the number of fires has declined). Very often, a fire will go to multiple alarms just to get more people. In Rochester, NY, where I live it's not unusual to see trucks arrive at the scene, park and all the firefighters get off and walk to the fire. The truck is simply used to transport them to the scene. All that said, the Brooklyn fire would still be freakin' huge, in any era.
posted by tommasz at 8:45 AM on May 3, 2006

Best answer: Howdy:

I'd have to do some research at home to answer your wildfire question, but in structural firefighting, as to the "alarm" classification, the short answer is "it depends".

The "alarm" level represents resources. For example, for a structure fire, each "alarm" will involve the response of a given set of resources such as an engine company, a truck company, a chief officer, medic units, and so forth and so on.

Each municipality will have an "alarm system" that's tailored to 1. their fire profile (how many fires they answer a year, what kinds of fires they tend to get, and the particular challenges they tend to face) and 2. their available resources (how many engine companies they have, and how many they can apply to a given fire without underserving the rest of their response area).

Often, alarm levels are also tailored to the size of the building and its composition: the first-alarm response for a shopping mall during business hours, for example, will be drastically greater in terms of resources assigned than that for a private residence.

So, the initial response (first alarm) is specific to the building, the type of fire, and the total resources that can be thrown at it.

Now, the determination on when to call a second, third, fourth or fifth alarm is usually a combination of the scene commander's discretion and procedure. Scene commanders tend to be, at a minimum, captains with many, many years of firefighting experience (on the first response), and most second alarms on up will have a chief-level officer in charge.

The scene commander pulls the trigger on escalating the alarm based on what they think it will take to get the fire under control: sometimes this will be procedural (if building is X size, and Y much is involved, call a second [third, fourth, etc] alarm), and sometimes it will be discretionary (the captain on the scene doesn't think they can get the fire under control with what they have).

Each increase in alarm level brings new resources to the fire: these will often be additional engine, truck or medic companies, but they frequently also include additional resources like air-resupply trucks (to refill air bottles), canteens (to feed the firefighters), and incident command vans to centralize the fire management in one place.

As for the "biggest and worst" question, as you can see from what I wrote earlier, it's going to be subjective. In terms of property and life lost, it's generally agreed that the San Francisco fire after the 1906 earthquake wiped out approximately 80% of the city, and killed several thousand people. The Great Chicago Fire in 1871 killed hundreds, and devastated Chicago.

To get a little less historical, the National Fire Protection Association considers the Oakland Fires to be number four on the list, right behind the WTC, San Francisco and Chicago.
posted by scrump at 9:04 AM on May 3, 2006

Best answer: Here is how the FDNY classifies the alarm levels of fires (it's by numbers of things/people dispatched):
posted by unknowncommand at 9:29 AM on May 3, 2006

Response by poster: Scrump, thanks for the awesome answer. That was exactly what I was looking for.
posted by disillusioned at 11:51 AM on May 3, 2006

And the Chicago way of doing things.
posted by @homer at 1:04 PM on May 3, 2006

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