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John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6 to garys_2k

Premium Member

to garys_2k

Re: smoke detectors

said by garys_2k:

No, dirty "air intakes" cause dirt to build up on the hvac unit's filter, heat exchanger, AC coil, ducts, etc. Smoke makes smoke detectors go off.

Not necessarily true.

It depends on the type of detector. Ionization detectors look at 'products of combustion' while photoelectrics look at particulates.
TheMG
Premium Member
join:2007-09-04
Canada
MikroTik RB450G
Cisco DPC3008
Cisco SPA112

TheMG

Premium Member

said by John Galt6:

said by garys_2k:

No, dirty "air intakes" cause dirt to build up on the hvac unit's filter, heat exchanger, AC coil, ducts, etc. Smoke makes smoke detectors go off.

Not necessarily true.

It depends on the type of detector. Ionization detectors look at 'products of combustion' while photoelectrics look at particulates.

I think what he's getting at is that air gets sucked into an air intake.

Having a dirty air intake/return is unlikely to have any effect on a smoke detector.

However, dirty dust-contaminated air being blown onto a smoke detector, can definitely lead to malfunction or false alarms in some cases.

John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6

Premium Member

said by TheMG:

I fully understand what he is asking.

Crap gets pulled into the combustion chamber which burns. Even though you cannot see it, the smoke detector does.

And, as lutful See Profile indicates, other non-combustion particulates can cause false alarms, depending on the detector.
TheMG
Premium Member
join:2007-09-04
Canada
MikroTik RB450G
Cisco DPC3008
Cisco SPA112

TheMG

Premium Member

said by John Galt6:

Crap gets pulled into the combustion chamber which burns.

No.

Combustion gases exit through the flue (chimney or exhaust pipe) to the outdoors. That is, unless there is something seriously wrong with the furnace. So even if the dust somehow does end up in the combustion air intake, the gases will be vented outside anyways.

If you're talking about dust hitting the heat exchanger and burning on the surfaces of the heat exchanger, you're using the wrong words. "Into the combustion chamber" implies that you are talking about the INSIDE of the heat exchanger, where the NG/LPG/OIL burns.

John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6

Premium Member

said by TheMG:

If you're talking about dust hitting the heat exchanger and burning on the surfaces of the heat exchanger, you're using the wrong words.

I acknowledge your more accurate representation of the inner workings and mechanism.
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

lutful

Premium Member

Click for full size
I just want to point out that lots of fine dust floating around by itself can cause photoelectric smoke alarms to trigger. This is purely because of light scattering physics. Labs actually test with "ISO fine dust" for calibration.