Brand
The default American CO alarm
The CO400 has 22,134 ratings, and the CO710 adds a display and a sealed 10-year battery.
Listings can be thin. The CO400 page says almost nothing, so read the model number and the manual.
Everything here comes from the Amazon.com listings of the products below, read from a New York address. Where a listing is silent, the review says so. Prices move, so use the live price on each review.
9V battery · electrochemical sensor · 7.2 oz · 10 to 95% RH
The default CO alarm: a simple 9V battery model with 22,134 ratings at 4.6 out of 5, with almost nothing written on the listing.
Best for: A second alarm near a stove or in a bedroom, on a budget.
≈ $22
plug-in · 9V backup · 85 dB · electrochemical · 3-pack · 7-year limited warranty
A 3-pack of plug-in alarms with 9V backup and a 7-year warranty, which covers a whole floor plan.
Best for: Covering each level and bedroom at once.
≈ $71
10-year battery · backlit display · shows CO and temperature · 85 dB · 6.4 oz
A sealed 10-year alarm with a backlit digital display, the kind of model to put near a stove.
Best for: The alarm nearest a wood stove, where you want to see a number.
≈ $44
smoke and CO · Precision Detection · battery · end-of-life warning · test/silence button
One unit for smoke and CO, with First Alert’s Precision Detection to reduce cooking false alarms.
Best for: A hallway where one combined alarm is the practical choice.
≈ $37
The price beside each product is fetched as this page opens, and it is the only figure here that is current. Any amount written into the prose was read once, on the day that sentence was written, and nothing has refreshed it since.
