The National Electrical Manufacturers Association (NEMA) has published NEMA WD 7 Occupancy Motion Sensors Standard.
Previously published as a guide and not a standard, WD 7 promotes uniformity for the definition and measurement of characteristics relevant to the use and application of occupancy motion sensors. This standard covers the definition and measurement of field of view and coverage characteristics relevant to the use and application of vacancy and occupancy sensors using individual or any combination of passive infrared, ultrasonic, or microwave technology. These sensors are used in systems for control of lighting, heating, ventilating, and air conditioning (HVAC), and other devices.
WD 7 may be downloaded at no cost here.