Optoma EH501 User Manual page 3

9. Moisture Condensation
Never operate this projector immediately after moving it from a cold
location to a warm one. When the projector is exposed to such a
change in temperature, moisture may condense on the lens and the
crucial internal parts. To prevent the unit from possible damage, do not
use the projector for at least 2 hours when there is an extreme or
sudden change in temperature.
EN-3