dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
1195
share rss forum feed


kkrrazy

@verizon.net

smoke detectors

Can dirty air intakes for your hvac unit cause the smoke detectors to go off???



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

I'll counter your overly generic question with an overly generic answer:

Smoke detectors go off when they detect what they are supposed to detect (whether it be smoke, or smoke-like-air).

Influenza & plague saturated air won't trigger a smoke detector.


garys_2k
Premium
join:2004-05-07
Farmington, MI
reply to kkrrazy

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.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6

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.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to kkrrazy

said by kkrrazy :

Can dirty air intakes for your hvac unit cause the smoke detectors to go off???

You are not supposed to place photoelectric smoke detectors close to the air return vents. Very fine dust blowing through the detection chamber may occasionally trigger an alarm.

P.S. Sometimes hotel maids trigger these alarms when flapping the bedsheets.

TheMG
Premium
join:2007-09-04
Canada
kudos:2
Reviews:
·NorthWest Tel
reply to John Galt

said by John Galt:

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 Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6

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.
--
Nothing makes an American want to do something more than telling them they can't.


Bob4
Account deleted

join:2012-07-22
New Jersey
Reviews:
·Optimum Online
reply to kkrrazy

said by kkrrazy :

Can dirty air intakes for your hvac unit cause the smoke detectors to go off???

No, but a dirty smoke detector can result in false alarms. Gently vacuum around the edge of your smoke detectors.


CKizer
Premium
join:2003-01-29
Tijeras, NM
kudos:2
reply to kkrrazy

Smoke detectors also need replacing about every ten years.


TheMG
Premium
join:2007-09-04
Canada
kudos:2
Reviews:
·NorthWest Tel
reply to John Galt

said by John Galt:

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 Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6

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
join:2005-06-16
Ottawa, ON
kudos:1

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.

garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
·callwithus
reply to kkrrazy

But, of course, none of this has anything to do with the OP's "dirty air intakes." Fine dust in the ambient air? Sure. Dirt on the air handler's intake grille, no. But yeah, of course, smoke IS fine particulates so any such particulates will seem like smoke to the detector.


Bob4
Account deleted

join:2012-07-22
New Jersey
Reviews:
·Optimum Online

said by garys_2k:

smoke IS fine particulates so any such particulates will seem like smoke to the detector.

Not to the ionization smoke detectors (the most common type).

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

said by Bob4:

said by garys_2k:

smoke IS fine particulates so any such particulates will seem like smoke to the detector.

Not to the ionization smoke detectors (the most common type).

That is a common misconception.

"Although this type of smoke detector is quite sensitive to small smoke aerosols, it is also sensitive to other particles that enter the ionization chamber, such as water droplets, dust, and other aerosols that unfortunately create nuisance alarms."

"Although optical smoke alarms are more immune to certain nuisance activation than ionization type smoke alarms because of their insensitivity of very small aerosols, they are generally slower to respond to fires that do not produce large-particle smoke."

Quotes from page 2/3 of the excellent report on present and future home smoke alarms by the US Consumer Product Safety Commission. »www.cpsc.gov/library/foia/foia12···larm.pdf