Cmd-2m marine carbon monoxide detector u.l. 1524 listed unit

SOURCE: smoke alarm/carbon monoxide detector

I have a First Alert Smoke Detector Model SA 86RAC.When I changed the Battery today it beeps.How do I fix this problem?

SOURCE: carbon monoxide detector err code

You are going to hate this as much as I did!
In the manual you will read this ..

Manual for Kidde Nighthawk C02 Detector
On page 13
----------------------------------
Unit Malfunction
In the rare event that your alarm malfunctions,
it will alert you with a short “chirp” and the red
LED will flash once every 30 seconds. The
digital model will display “Err” as shown in
Fig. 6.
Seven years after initial power up, this unit will "chirp" every
30 seconds to indicate that it is time to replace the alarm.
The unit will not detect CO in this condition. Please replace
immediately.

SOURCE: Our carbon monoxide detector keeps beeping every

Need new detector

SOURCE: My nighthawk Kidde carbon monoxide detector keeps

Some models of Carbon Monoxide Detectors will give an audible beep every 25-30 seconds after it has sounded an alert alarm. This may have happened when there was noone home to hear it. A periodic beeping sound may also indicate it is time to change the battery.

Solution: Install a new battery and check your manual for instructions on how to reset the system. Check the expiry date on your unit, it needs to be replaced after 5 to 7 years, according to the manufacturer specifications.

If you are in doubt that your Carbon Monoxide Detector is not working effectively, REPLACE IT. Your safety and your peace of mind is worth it.
View most Brands and Models of Carbon Monoxide Detectors online.

SOURCE: our kidde battery operated Carbon Monoxide

Relocate it to an area of fresh air - outside will work.. Does it still beep?
If yes, recover the new battery and toss the unit.

Do you have it located in a steamy damp area? Laundry room, bath room etc.. That will cause it to malfunction too..