There are several factors to take into account when placing a PIR on your property to avoid unnecessary false alarms.
The most common cause of false alarms is foliage or moving branches so make sure there are no bushes or trees within the detection range of your PIR. You can fit the occluder supplied for the tops of bushes etc.
Another cause is white light blinding the detector. EasySwitch detectors are fitted with filters but avoid fitting them facing glass as this will affect their performance.
Avoid placing detectors above or in the path of air vents as this causes air convection within the housing.
In terms of mounting height, the best position is between 2 and 2.5 metres from the ground. You should mount the detector so that people walk across the direction in which the detector is pointing. If someone moves towards or away from the detector the detection range is reduced.