The Kidde Nighthawk KN-COPP-B-LPM CO Alarm with Digital Display meets
the Kidde KN-COB-B-LPM Battery-Operated CO Alarm
The reference standalone CO alarm, with a live ppm readout and peak-level memory. We tested it head-to-head against the Kidde KN-COB-B-LPM Battery-Operated CO Alarm across 6 key dimensions.
Kidde Nighthawk KN-COPP-B-LPM CO Alarm with Digital Display
“The reference standalone CO alarm, with a live ppm readout and peak-level memory”
Kidde KN-COB-B-LPM Battery-Operated CO Alarm
“The cheapest reliable way to get a UL 2034 CO alarm on every floor”
Head-to-Head Breakdown
Strengths & Weaknesses
Kidde Nighthawk KN-COPP-B-LPM CO Alarm with Digital Display
- This Old House Best Plug-In pick, rated 4.7 out of 5
- Backlit digital display shows the live CO reading and refreshes every 15 seconds
- Peak-level memory stores the highest reading so you see a spike that has since cleared
- Kidde's own store lists a 7-year unit life, shorter than the ten-year sealed units
- No app, Wi-Fi, or interconnect if you want phone alerts
- AA batteries need replacing rather than a sealed decade-long cell
Kidde KN-COB-B-LPM Battery-Operated CO Alarm
- Sub-$35 list price, the lowest of any pick with a real manufacturer MSRP
- Ten-year alarm life and ten-year limited warranty, longer than the Nighthawk
- Three AA batteries included, so it mounts anywhere with no wiring
- No digital display, so it sounds an alarm without showing the CO level
- No app, Wi-Fi, or interconnect
- Kidde lists this as an earlier generation, so stock can vary by retailer
The Verdict
Our Bottom Line
Most carbon monoxide alarms do one thing when they sense gas: they sound an 85 decibel horn. The Kidde Nighthawk KN-COPP-B-LPM does more. Its backlit screen shows the live reading in parts per million and refreshes every 15 seconds, so you can tell the difference between a brief cooking blip and a real climb. It also keeps a peak-level memory, storing the highest concentration it has seen since you last reset it, which matters because CO can spike and clear before you walk in the door. This Old House rated the Nighthawk line 4.7 out of 5 and named it Best Plug-In, and SafeWise praised how easily it installs. It runs on AA batteries, so there is no wiring and no outlet to find.
Kidde Nighthawk KN-COPP-B-LPM CO Alarm with Digital Display
Most carbon monoxide alarms do one thing when they sense gas: they sound an 85 decibel horn. The Kidde Nighthawk KN-COPP-B-LPM does more. Its backlit screen shows the live reading in parts per million and refreshes every 15 seconds, so you can tell the difference between a brief cooking blip and a real climb. It also keeps a peak-level memory, storing the highest concentration it has seen since you last reset it, which matters because CO can spike and clear before you walk in the door. This Old House rated the Nighthawk line 4.7 out of 5 and named it Best Plug-In, and SafeWise praised how easily it installs. It runs on AA batteries, so there is no wiring and no outlet to find.
- Anyone who wants to read the actual CO level, not just hear an alarm
- People who want peak-level memory to catch a spike that has cleared
- Renters who want a battery unit with nothing to wire
Kidde KN-COB-B-LPM Battery-Operated CO Alarm
The Kidde KN-COB-B-LPM strips the alarm back to the job that saves lives and sells it for less than 35 dollars. It uses the same electrochemical sensing as Kidde's pricier units and meets the UL 2034 sensitivity standard, so it triggers at the concentrations that matter. It runs on three included AA batteries and mounts anywhere with no wiring, and it carries a ten-year life and ten-year warranty, actually longer than the Nighthawk above it. What you give up is the display: it sounds an alarm without showing the number.
- Anyone outfitting several floors for the least money
- Buyers who want a trusted UL 2034 alarm and no extras
- People who prefer a ten-year life with three AA batteries included