Press black button and hold until display tells you to release. Turn unit on in a clean-air environment. Press mode button at display prompt. Red lights flash and unit beeps.
Beeps are more frequent at higher contaminant levels, or lower oxygen level.
Example of a clean air display. CO and H 2 S are in ppm, O 2 and LEL readings are percentage values. Use the PEAK function to display highest recorded readings for CO, H2S, and LEL, and the lowest reading for O2. Readings are not erased when you turn the unit off. You must use the Peak Clear function to erase the memory.