Kidde Plug-In Carbon Monoxide Detector w/ Battery Backup Expired

Firefighter here. I just want to confirm that these answers are absolutely correct. Any house using natural gas (generally methane) or propane should have explosive gas alarm(s) in addition to carbon monoxide detectors. Carbon monoxide is created by partially burned fuel releasing CO instead of CO2, and its source can be anything from a faulty pilot light, to a running car in an attached garage, to burning embers in the bottom of an ash bucket next to a wood stove (which can still generate enough CO to kill). It is colorless, odorless...undetectable except by carbon monoxide detectors. Honestly, every house should have at least one CO alarm, even if there aren't any presumed sources.

Explosive gas will not trigger carbon monoxide detectors, even at high concentrations. Usually people rely on the bad smell (like rotten eggs) that is added to natural gas/propane as a warning system. However, we have seen situations where gradual accumulation prevented detection due to nose blindness. A few years ago a man and woman came home from date night and could smell natural gas in their driveway as they pulled up. Their two teenage boys were at the back of the small house (1500 sq ft) playing video games and hadn't noticed a thing. One of them had nudged a kitchen stove burner knob and it was hissing out gas, filling the house. After that, they got one of the these alarms [amazon.com] and put it in their kitchen. Tested by leaving a burner slightly on, unlit...the alarm went off in under five minutes. I have the same unit in my own kitchen.

One last important point: if you smell gas in your house, do not start opening windows to air it out. Explosive gasses are only explosive at relatively low concentrations with air. Propane is only about 10%; methane around 15%. By the time you smell it, it's possible your concentrations could be higher than that. Opening windows could pull you back into the "danger zone". Don't ventilate; evacuate. Call the fire department. We can determine the concentrations and ventilation needs, as well as speed ventilations with fans that are low-risk for causing explosions.

Remember, as a general rule (in the US at least):
• We won't charge you for our help
• You are not bothering us
• If anything, you are probably making our day more interesting
• It is good practice for us
• We are then on-hand in case anything does explode

Alright, enough rambling from me. Be safe, everyone.

In case anyone is wondering where to place these -

Per EPA.gov

Carbon monoxide is actually slightly lighter than air.

https://www.epa.gov/indoor-air-qu...e-detector