Ionization smoke detectors

[nscherneck]

This may not pertain directly to an NFPA standard, but I feel this is the most appropriate forum to ask in...

I came across a note in a NICET study guide that stated that ionization smoke detectors are affected at elevations above 3500'. This was interesting to me as i recently had trouble with ionization detectors at a project at the volcano on the big island (about 4500'). Anyone know anything about why ions are affected above 3500'? I understand that air is thinner at higher elevations, but why does that affect ionization smoke detectors?

Thank you

Nathan Scherneck, NICET II (fire alarm)
National Fire Protection
Honolulu, HI

 

[cdafd]

Have you checked the manufacture's specs for what altitude they are listed to??

 

[DonPhillips]

Perhaps the reduced air density at higher altitudes?

Don Phillips

http://worthingtonengineering.com

 

[cdafd]

Due to their operating principles, they offer limited capabilities when installed in high altitude locations

 

[cdafd]

From the good Doctor:


As you know, ionization smoke detectors (alarms) use a small amount of radioactive material to ionize the air in the sensing chamber. As you go up in elevation, the thinner atmosphere allows more natural radiation to reach the earth surface or in this case the smoke detector or alarm sensing chamber. This increased natural radiation could affect the sensitivity or operation of the device.

One method of addressing this issue is for the device to incorporate two chambers. One is used as a "reference" and this other is the actual detection chamber. This allows the device to adjust for the normal background conditions.

Many of the manufacturer's address installations in higher elevations in their smoke detector data technical data sheets.

A quick google search will find that this is a concern with ionization detection devices used in the aviation industry. Hope this helps.
--
If you have to call 9-1-1, it's
too late.

Dr. James G. Munger, Ph.D,
MIFireE, CFPS
KI4ZKQ
James G. Munger and Associates,