Formaldehyde Monitor Detector (Battery Operated) with Alarm for Home and Outdoor Use LCD screen with bright backlight for convenient of use in low light areas. An ideal tool to monitor the formaldehyde concentration at home, office or inside your car HCHO (Formaldehyde) + TVOC (Total Volatile Organic Compounds) level readings. Real time monitoring of in-door formaldehyde concentration with audible / visual alarms. Measurements measured in mg/m3