BTW those of you who want leave the house when it is on, if it did catch fire what are you planning to do? If it started smouldering are you regularly within sniffing distance. Personally I would be more concerned about running the dryer when I went to bed.
Smoke detectors and smell would be the primary warning. And, yes, I'd investigate and if the fire was confined to the dryer cabinet I'd probably have a go at puting it out after everyone was out of the house. I'd guess the 10 lb dry chemical extinguisher blasted into the dryer exhaust port outside the house would knock things down quite a bit, and I might have a go with a garden hose after shutting off all power to the house. At least it would keep me busy until the fire department arrived. Best of all. I'd have a story to tell later.
The most frequent (but not most serious) fires onboard my submarines came from the ship's laundry dryers-- lint in the heater coils. The stench is unbelievable (the burning lint, not the laundry) so "sniffing distance" is probably measured within tens of feet. Usually the combustion is occurring near the dryer's electric heating coils, not in the (plugged) exhaust hose, so popping the breaker and clearing the scene is all that's necessary.
The "approved" extinguishing agent would be CO2, but one of those home multi-purpose powder extinguishers would work just fine if no one else needed to dry their wet laundry anytime soon. I wouldn't be very enthused about attacking an electrical fire with a water hose unless I was sure that I'd removed all the power. Even then, knowing my luck, I'd ground out a capacitor. But a water hose is better than nothing and I've never known anyone killed by the shock.
My last military job was at a training command that included a fire trainer. It was fueled by propane and filled with sensors. For max realism, the trainer's performance was based on Naval Research Lab test data from an instrumented (decommissioned) submarine hull. To put out a fire in the trainer, you had to apply the proper extinguishing agents at the correct locations for at least a minimum amount of time or the computer would keep the fires burning. It really drove home the submarine firefighting concept of "stand and fight".
One of our instructors lived in the end unit of a base-housing quad. One evening his neighbor at the other end of the quad set his kitchen on fire (dinnertime) and the smoke detectors alerted everyone. Jake's instinct was to see if anyone needed help, and when he arrived the fire was really just getting going. He grabbed a garden hose and started fighting the kitchen flames from the yard, having things all to himself during the 10 minutes it took for the fire crew to arrive. It cost him his eyebrows and his forearm hair, "as usual", but he saved the rest of the structure.
No one was hurt. It turned out that the dinner chef had a pan fire that he tried to put out with an extinguisher, splattering the flaming oil all over the kitchen. If he'd just had the presence of mind to shut off the burner and put a lid on the pan it would've saved his family a couple weeks of hotel living.
And yes, my kid and I have practiced her extinguisher technique on our BBQ and her pan-lid technique in the kitchen...