Extech irt600 infrared thermal condensation scanner extech irt600 p the extech instruments irt600 is an infrared thermal condensation scanner which is capable of displaying air temperature at surface temperature st relative humidity rh and dew point temperature dp and can analyse the potential for mildew p p the led lamp above the lcd display changes colour to indicate the potential for mildew green no mildew yellow or amber low to moderate probability of mildew and red