Several guidelines have been set in place for IAQ monitoring. They mostly include placing the monitors in the height of a typical breathing zone and away from openable doors and windows. The US EPA guide states that the ideal placement would be at a height of 0.9 -1.8 m and away from pollution sources and sinks. Rapid changes in temperature and relative humidity should be avoided near the sensors and one should make sure the sensors are not tucked away behind furniture .