Smoke alarm/co sensor.

[oldwino]

Inspired by SJKent’s post about hard wiring detectors there is something I don’t understand. They’re making combo units that detect smoke and CO. If Carbon Monoxide hangs low to the ground and smoke rises how would you mount the combo units?

 

[rlitman]

CO doesn’t seek the floor. It’s roughly the same density as air and can be found anywhere in the room.

 

[Kevin Essiambre]

Inspired by SJKent’s post about hard wiring detectors there is something I don’t understand. They’re making combo units that detect smoke and CO. If Carbon Monoxide hangs low to the ground and smoke rises how would you mount the combo units?

Carbon Monoxide had a density similar to air at room temperature. At 0°C (32°F) it's heavier.

The density of Carbon Monoxide at 20 °C (68 °F) is 0.96716 which is slightly lighter than the density of air (1.00)

Source: Google and experience.

Sent from my SM-G920W8 using Tapatalk

 

[SGKent]

I can attest to what Ritman and Kevin said. The 77 VW bus engine was idling one day with the garage to house door open. The exhaust pre-catalytic converter is 1% CO. Post-catalytic converter it is .00% CO to .01% CO based on the smog tests, and my own equipment. That was enough to set the CO detector off down the hall on the ceiling 30' from the tailpipe. The Acura is ULEV-2 or something like that and it is like .00000000% CO so it won't set off the alarm.

 

[oldwino]

Thanks, guys. Guess I was wrong

 

[Git]

This is from the instructions that came with my First Alert combo

 

[SGKent]

2nd roofing contractor was out today. He said that the current inspectors are looking for a CO detector to be lower near the floor. He uses ones plugged into a wall socket. He said that the inspectors here have been flunking ones on the ceiling. Just an FYI. I would think it would be the other way around but not so.

 

[rlitman]

2nd roofing contractor was out today. He said that the current inspectors are looking for a CO detector to be lower near the floor. He uses ones plugged into a wall socket. He said that the inspectors here have been flunking ones on the ceiling. Just an FYI. I would think it would be the other way around but not so.

Probably a misinterpretation of the instructions. The inspector doesn't get to set the location, only the manufacturer does with their UL listing.

That being said, corners of ceilings are verboten for CO detectors, due to lack of air flow. The middle of a ceiling is just fine.

 

[Git]

2nd roofing contractor was out today. He said that the current inspectors are looking for a CO detector to be lower near the floor. He uses ones plugged into a wall socket. He said that the inspectors here have been flunking ones on the ceiling. Just an FYI. I would think it would be the other way around but not so.

I would think it would be hard to go against the manufacturers' recommendations... I would follow the instructions that come with the unit

For example - who would have thought?

"Do not install this unit over an electrical junction box. Air currents around junction boxes can prevent smoke from reaching the sensing chamber and prevent the unit from alarming. Only AC powered units are intended for installation over junction boxes"

and there is a whole list of place where not to install:

WHERE THIS ALARM SHOULD NOT BE INSTALLED
Do NOT locate this Smoke/CO Alarm:
• In garages, furnace rooms, crawl spaces and unfinished attics. Avoid
extremely dusty, dirty or greasy areas.
• Where combustion particles are produced. Combustion particles form when something burns. Areas to avoid include poorly ventilated kitchens, garages, and furnace rooms. Keep units at least 20 feet (6 meters) from the sources of combustion particles (stove, furnace, water heater, space heater) if possible. In areas where a 20-foot (6 meter) distance is not
possible – in modular, mobile, or smaller homes, for example – it is recommended the Smoke Alarm be placed as far from these fuel-burning sources as possible. The placement recommendations are intended to keep these Alarms at a reasonable distance from a fuel-burning source, and thus reduce “unwanted” alarms. Unwanted alarms can occur if a Smoke Alarm is placed directly next to a fuel-burning source. Ventilate these areas as much as possible.
• Within 5 feet (1.5 meters) of any cooking appliance. In air streams near
kitchens. Air currents can draw cooking smoke into the smoke sensor
and cause unwanted alarms.
• In extremely humid areas. This Alarm should be at least 10 feet (3 meters)
from a shower, sauna, humidifier, vaporizer, dishwasher, laundry room, utility room, or other source of high humidity.
• In direct sunlight.
• In turbulent air, like near ceiling fans or open windows. Blowing air may
prevent CO or smoke from reaching the sensors.
• In areas where temperature is colder than 40˚ F (4.4˚ C) or hotter than 100˚F (37.8˚ C). These areas include non-airconditioned crawl spaces, unfinished attics, uninsulated or poorly insulated ceilings, porches, and
garages.
• In insect infested areas. Insects can clog the openings to the sensing chamber.
• Less than 12 inches (305 mm) away from fluorescent lights. Electrical
“noise” can interfere with the sensor.
• In “dead air” spaces. See “Avoiding Dead Air Spaces”.

 

[SGKent]

Ya know, I really don't feel like arguing with an inspector. If they want a CO unit that plugs into a wall receptacle I'll do that to make the final simpler.

 

[Git]

I can't help but think that if you buy a detector that plugs into an outlet, your pretty limited where you can use it - I don't think I ever saw an outlet up by the ceiling....

Instead of listening to this 'roofer' - why not just call your building department, they have seemed to be helpful so far

 

[SGKent]

I can't help but think that if you buy a detector that plugs into an outlet, your pretty limited where you can use it - I don't think I ever saw an outlet up by the ceiling....

Instead of listening to this 'roofer' - why not just call your building department, they have seemed to be helpful so far

I really hate to keep bothering these folks down at city hall but I got a hold of them and they said the combo one on the ceiling now is good enough. So Git, you saved me $30.

 

[Git]