I was finished taking a shower downstairs and my upstairs smoke alarm went off. It is located directly under the hatch that leads to the roof. I put the exhaust fan on in the bathroom, and nothing happened. It was 74 degreess in the house and about 99 degrees outside. When I opened the roof hatch my glasses steamed up so bad that my hair dried and my whole face was dripping wet from the heat in the attic. I do believe the attic was so hot it caused the smoke alarm to go off. The alarm goes off sometimes when we take a shower upstairs, but not downstairs.

Has this ever happened to anyone on a hot day? I had to raise the AC thermostat to 72, and put 2 fans near the hatch to let the heat escape from the attic. This was a good wakeup call to open that hatch now and then to let the heat out.:eek:

The culpret is dew point and the type of smoke detector. There are two types of smoke detectors, one is photoelectric (cheaper) and one is ionization (more expensive, accurate and slightly radioactive). Talc, dust and steam will set off a photoelectric detector. It will not set off an ionization detector. Photo electric detectors need to be cleaned ocaisionally with canned air.

It's likely that the temperature of the detector is somewhat cold and the 99 F heat was very humid. This caused condensation which was interpreted as smoke.

If you look at the Farenheight Dew point table here:

LAMTEC - Dew point calculator (http://www.lamtec.com/dew-point-calculator.htm)

From this table if the air temperature was 100 deg F and 75% RH, condensation would occur at 91 degress or lower. I'm assuming that your air temp is 100 rather than 99 and has an RH of 75%. If the interior temp is 72, it's going to condense because it will start condensing at 91 F.

So that's what's happening. Fixing the air leak in your hatch might prevent one of the false alarms. Relocation might fix the shower false alarms. Changing to an ionization detector will fix both problems. The attic should have a heat sensor. Proper ventilating an attic is always a good idea.

So that's what's happening. Fixing the air leak in your hatch might prevent one of the false alarms. Relocation might fix the shower false alarms. Changing to an ionization detector will fix both problems. The attic should have a heat sensor. Proper ventilating an attic is always a good idea.

Thank you very much for your advise and information. I am sure the attice was well over 99. We will have to look into getting better ventilation and a ionization detector.

I see you already have a solution.

i see you already have a solution.

Well as of now, the summer is almost over and that heat spell we had is over. We did not change the location of the smoke detector because now we know it works. It actually is in the hallway of our bedroom, and we could escape out of our window in case of a real fire. If that much heat comes from the attic we really SHOULD be alerted. We will have to wait until the spring before we do anything about the ventilation. We already have 2 large vents (looks like 3' X 2' ) located on the north and south sides. They are covered with a plastic shield so the rain can't get in. I really don't know what else we can do. It is not a walk in attic. It is pitched and we store some boxes up there. Our home was built in 1989. I guess we need more vents.

DON'T EVER cover the vents with plastic. It can cause lots of damage due to condensation in the attic. It can damage the insulation and cause spots on the ceiling. The nails from the shingles can drip.

A ridge vent goes across the top of the roof assuming an "A" frame roof. They are easy for your roofer to put in when you re-shingle.

An attic fan which are normally temperature controlled is a great way to ventilate the attic.

Remove the plastic covering the vents ASAP. Don't even cover them in winter.

Your problem with the smoke detector may go away by just by uncovering the vents.

DON'T EVER cover the vents with plastic. It can cause lots of damage due to condensation in the attic. It can damage the insulation and cause spots on the ceiling. The nails from the shingles can drip.

A ridge vent goes across the top of the roof assuming an "A" frame roof. They are easy for your roofer to put in when you re-shingle.

An attic fan which are normally temperature controlled is a great way to ventilate the attic.

Remove the plastic covering the vents ASAP. Don't even cover them in winter.

Your problem with the smoke detector may go away by just by uncovering the vents.


The plastic is not stationary. It flaps. I wonder if there is a way I can keep them open by a hook or something, no one ever told us. But I certainly will look into it. You are once again giving me very good help and I appreciate it. I will check it out and let you know.

Here is a reference:

ATTIC VENTILATION (http://www.accurateinspection.com/Attic%20Ventilation.htm)