I've been a volunteer firefighter for going on 14 years now, here is one of my more memorable fires.
Living in the northeast we get alot of calls for chimney fires - usually they are not a big deal. You go in the house with a big metal bucket, pull the logs out of the fire and let everything cool off, the fire (in the chimney) will usually go out by itself. Usually the cause of such a fire is creosote buildup (from no or poor cleaning).
So one night we get a call for a chimney fire at an address fairly close to the station. I don't remember if I was at the station or home but I was on the first Engine out that night. While we are enroute to the call I have the same old (another crappy call) thought that you get after going to countless BS calls (most of the calls are BS) so I'm not paying too much attention to the radio noise in the background.
I start to notice that my partner seems to be getting rather concerned about something so I start listening to the radio transmissions. There is a chief on the scene reporting a light smoke condition (nothing abnormal) a few moments later he radios that the siding on the back side of the house is melting off and where/who is the closest Engine (we respond from multiple stations so it could be coming from any or all of 3[now 4] stations) Turns out we are first due and he gives instructions to the officer to pick up a Hydrant and then bring a line (fire hose) in the front door and up-stairs. The funny thing about this is most fireplaces are on the ground floor or in the basement, rarely do you find one on the second floor.
We arrive on-scene, pull a line off the engine and start taking it in the front door and then up the stairs. My partner is the nozzle man and I am his backup. As we are moving up the stairs I notice only a very light smoke haze, nothing more than what burning toast would give off. We get to the top of the stairs and the chief meets us there and tells us to "mask up" (put on our facemasks and air so we can breathe in smoky environments) - I'm thinking to myself, WTF, theres hardly any smoke here. We are instructed to take the line through the room on the left and into an adjoining room. By now the Truck crew has arrived and 2 of their guys are upstairs with us (and we're all masked up, in a very light smoke condition). We proceed into the next room and are told to hold at that position and get ready (at that time the line was finally charged with water and brought up to pressure - 200 psi) so we get down on our knees (because smoke rises) and get a good grip on the hose. The boys from the Truck start pulling clothes and shoes out of the closet (and I'm still thinking WTF is going on here).
Pretty soon one of them steps away and kneels down, the other guy picks up his axe, turns to us and says "You ready?" we nod yes so he starts swinging at the wall in the back of the closet. He takes 2 shots at that wall and within 2 seconds we go from a normal environment into hell.
The first thing I see is a huge ball of flame shoot out of that hole, up the side of the wall, out of the closet door and start rolling over our heads. Almost instantly after that dark brown, almost black, smoke fills the room and drops to about 12 inches from the floor. We go from good visibilty to zero, in the blink of an eye. My partner releases the bail on the nozzle and we start pouring water in the general direction of the closet (which we now cannot see). It finally dawns on me that I need to direct him, so I bend my head down to the ground and am able to see (under the smoke) to where the closet is. We advance toward the closet and pretty much flood the area with water. After a short time we shut down the nozzle so we can access the situation.
So, I'm sitting there in the blackness of the smoke with my partner, listening to the drip drip of water while the other 2 guys try to figure out if we have gotten all the fire. Pretty soon I hear a chainsaw from up above, notice that the smoke is getting lighter and then start feeling something light falling on to my helmet. Visibility starts to get better so I'm able to look up and see whats falling (cellulose insulation from the attic) and look directly into the face of a firefighter smiling down at me through a hole in the ceiling/roof. I give him a "thumbs up" and we then stand up and finish extinguishing the few remaining hot spots.
Shortly after that we are sent outside with the other 2 guys that were with us to "rehab". Outside we give each other some "high fives", get some water and then start talking about what the four of us just went through.
This whole thing - from initial alarm to the "rehab" point took maybe 15 minutes or less.