Very pleasantly surprised by this little gadget. Very easy to use, easy to read and it seems accurate (how do you really know?). When testing it outdoors it showed similar results as published air quality for my location. It responds quickly to changes in air quality (blow out a candle and it goes crazy!) and with the built in battery it is easy to move around your house to check each room. Battery seems to last about the 6 hours advertised, just be aware that the battery strength bars disappear more quickly as it gets empty. The display is very bright, and it would actually be nice if it had a dimmer for use in a bedroom at night. The red / yellow / green indicator is helpful, although you have to look closely to see the difference between yellow and green.
All in all, a nice and affordable air quality monitor. Glad I did not spend more money , this does the trick!