Product review (5 stars): EXCELLENT product. Examples I discovered
Very fast tracking of CO2 levels. EXCELLENT product. Examples I discovered: As soon as you enter a room with the monitor, the levels start to rise from your own breath. If you want uncontaminated data of the baseline level of a room's ventilation, you have to set the sensor in the UN-occupied room and IMMEDIATELY leave the room, preferably closing the door behind you, wait a few minutes, then re-enter the room and check the reading immediately before it goes up.
 I found my breathing raised my home-office or my bedroom by about 300 PPM after the room had been vacant for about 8 hours. This is due to no mechanical air flow fan moving air in the house. For best quality/healthy sleep levels, I highly advise sleeping with your bedroom door open. If two folks are sleeping the the same bedroom with the door closed, you most surely are above the unhealthy 1100 PPM and may be suffering from lack of motivation, tired days, and possibly heart murmurs. Everyone should have one of these in the house. Everyone should also have an ERV (Energy Recovery Ventilator) which brings in fresh air from outside. GOOGLE it.