How to Use the Test Button
Any time you push the Test/Reset button, the alarm will go through a series of test numbers that are programmed into the unit to test the internal diagnostics. This will start with an 888 reading, then display numbers usually in the 200 range, then back to 888, and lastly to zero. These are not actual readings, so you don't have to be alarmed or take action.
What Is Peak Level?
The Peak Level reading is just a memory. At one point, the unit was exposed to something that caused the reading. It could have been a substance that was sprayed too close to the unit, paint fumes, or actual carbon monoxide that caused the reading.
To reset the peak level memory, push the Peak Level button and hold it down while you press and hold the Test/Reset button for 2 seconds, then release them at the same time.
After this, monitor the unit for a few days to determine if this is a recurring problem or if it was an old reading. If you don't get a reading, then you know it could have just been a random reading and you have no other event taking place. If a reading does come back, reset the peak level again and start watching it every one to two hours to try to narrow down when the reading is happening and be aware of what's going on around you (heat coming on or off, cleaning, etc.) to determine the source of the reading.