What makes Smoke Alarms go off? (besides smoke)

If it has a carbon monoxide detector....or

The battery is low.....

steam from my shower has set off the one in the hall before

steam can make some go off. depends on id your are using ionization or photelectric

Steam, dust, and heat all can set off fire alarms

Mine are just plain smoke alarms. Usually they chirp when the battery is low. Yesterday, and now they went off like there was smoke. I hear one going off outside, too.

A low battery should only make them beep intermittently, are you in an area where there is natural gas pipping?

HAARP

Well in that case I would go ahead and soak the joint just in case, after you turn off the main breaker of course.

heh - guess I'll hose down all the neighbors houses, too.

Cooking with the windows closed usually

Me having smoking hot sex.....ow wait...that's smoke...

Smoke Detectors:
There are three basic types of residential smoke detectors, all with different means for detecting smoke and fire, different types of fires they detect best, and different replacement reasons & needs.

Ionization Smoke Detectors powered by batteries are the most common kind and economically available at most local hardware and discount stores. They can be mounted easily in just about any location. They use a small radioactive source (not harmful to humans) to cause the air inside the detector to be capable of carrying electric current.
As particles of smoke enter the detector they block the flow of electricity. Low electrical current causes the alarm to sound. These detectors work best on flaming type fires (wood, paper, etc) and react a little slower on smoldering fires (mattresses, couches, etc). Batteries need to be replaced occasionally.
If your detector starts making a chirping sound every so often, you need to change the battery. A general recommendation is to change these batteries every six months, usually timed to a major event like springing forward to daylight savings time or falling back to normal time. (Some newer smoke detectors come with a 10 year Lithium battery that eliminates the need to change batteries.) Remember battery powered detectors operate even during power failures.

Photoelectric Smoke Detectors use a light sensitive photocell to detect smoke inside the detector. They usually require a connection to an electrical supply but are also available with a battery backup.
A light bulb puts out a beam of light. The photocell is hidden from direct exposure to the light beam. Smoke entering the detector causes the light beam to be reflected in several directions. The photo cell detects the reflected light and causes the alarm to go off. These detectors work best on smoldering fires and react a little slower on flaming type fires. The light bulbs need replacement every few years.

Thermal Detectors usually requiring a connection to an electrical supply, react to heat rather than smoke. A fire must raise the heat level near the detector to cause the alarm to go off. This type of detector is mostly used in dusty, dirty environments usually found in industrial and commercial applications. This is the type of detector that most fire sprinkler heads use to detect heat, pop, and start spraying water. This detector would be good near a cooking stove where an ionization or photoelectric smoke detector might cause false alarms.

It is my observation that the dying gasp low battery alarm always goes off during the middle of the night.

i was gonna say that

Isn't that the truth...never fails!!!

Spraying air freshener set mine off once!

Must be the steam from the warm, humid wind and massive rainstorm that came up from Flori-duh. Hope it didn't bring corexit up with it.
The northeast has flood warnings all over from this storm.