Review on SEAAN Formaldehyde Portable Detector: Advanced Recording Technology for Chemical Safety by Michael Vargas

Works right out of the box. Never read the manual, but it's easy; just turn it on. Some values appear immediately. Others, like CO2, take up to a minute to appear, likely because CO2 is measured in parts per million. There are green, yellow and red air quality indicators at 6 different levels. 4 digit precision. Most plants grow in proportion to the 150 ppm shift in CO2 concentration, where all growth stops. So this comes in handy in a greenhouse to ensure the plants are saturated.