Any time you push the Test/Reset button, the unit will go through a series of numbers that are programmed to test the unit's internal diagnostics. This will start out with an 888 reading, then display numbers usually in the 200 ranges, then back to 888, and back to zero. They are not actual readings, so you should not be alarmed and do not need to take any further action.
When 200 Appears on Your Carbon Monoxide Alarms Display
October 4, 2019