True. I was speaking loosely. 50 is OSHA limit for 8 hour exposure. A minute or two at 80, I would think is VERY unlikely to cause any symptoms. So if it was from the direction wind was blowing during run-up, not a problem. If it doesn't go right back to low levels, then there's a problem. If it happens again, there's a problem.
CO is not something to be messed with. I am NOT minimizing its importance. It CAN be deadly. I'm just saying one TRANSIENT reading of 80 is not necessarily an indication of a huge problem. Definitely needs to be monitored. If it returns to 0 and doesn't happen next run-up, it MAY have been wind blowing in exhaust. Definitely needs to be monitored closely.
https://www.osha.gov/OshDoc/data_General_Facts/carbonmonoxide-factsheet.pdf
What are the OSHA standards for CO exposure?
The OSHA PEL for CO is 50 parts per million (ppm). OSHA standards prohibit worker exposure to more than 50 parts of CO gas per million parts of air averaged during an 8-hour time period.
The 8-hour PEL for CO in maritime operations is also 50 ppm. Maritime workers, however, must be removed from exposure if the CO concentration in the atmosphere exceeds 100 ppm. The peak CO level for employees engaged in Ro-Ro operations (roll-on roll-off operations during cargo loading and unloading) is 200 ppm.
https://www.kidde.com/home-safety/en/us/support/help-center/browse-articles/articles/what_are_the_carbon_monoxide_levels_that_will_sound_the_alarm_.html
Carbon Monoxide Levels and Their Symptoms
IMPORTANT: If your carbon monoxide alarm sounds, or you suspect you are experiencing symptoms of carbon monoxide poisoning, you should immediately leave your home and call 9-1-1.
50 PPM
None for healthy adults. According to the Occupational Safety & Health Administration (OSHA), this is the maximum allowable concentration for continuous exposure for healthy adults in any eight-hour period.
200 PPM
Slight headache, fatigue, dizziness, and nausea after two to three hours.
400 PPM
Frontal headaches with one to two hours. Life threatening after three hours.
800 PPM
Dizziness, nausea, and convulsions within 45 minutes. Unconsciousness within two hours. Death within two to three hours.
1,600 PPM
Headache, dizziness and nausea within 20 minutes. Death within one hour.
NOTE: For more information about your specific alarm, refer to your user’s manual.