Qooarker Air Quality Detector - Accurate Testing Formaldehyde(HCHO) Monitor also PM2.5/PM10,TVOC Test Air Quality Meter with Time Display for Car Indoor Detection Outdoor Detection

Needs time to calibrate but works great

I received the item today, put in batteries and turned it on. After the 180s preheat, it started measuring and the alarm went off, while the screen was showing high levels of formaldehyde and TVOCs. I turned it off and in a couple of minutes tried the measurement in another room, same result. Then the measurements started decreasing and in a few minutes the device showed only minimal levels. I repeated the measurement a few hours later and the levels shown remain minimal. I really don't know what to think. Are the levels high and the sensor is saturated and no longer able to measure or are they low and the first few measurements were somehow a side effect of packaging and shipping or of being new. In short, using this device really didn't tell me what I needed to know. Importantly, the device is showing the room temperature as 26oC, but two thermometers and a thermostat show 21oC. If it can't even measure the room temperature, I really doubt that it can make more challenging measurements.