How many PIR sensors do I need for a room?

A standard wall-mounted PIR covers roughly 50 m² after real-world derating (110° wedge × 10 m range, minus 20% for dead zones near walls). Rooms up to 50 m² typically need one sensor — but always add one extra per entrance after the first. Ceiling-mounted 360° sensors cover ~105 m² each. Use the calculator above for room-specific numbers.

Should I use wall-mount or ceiling-mount PIR sensors?

Wall mount is best for corridors, entries, and long approaches — the wedge pattern catches motion crossing the room. Ceiling mount gives more uniform coverage in open spaces (showrooms, lobbies) but needs more sensors per m² in narrow rooms because the circle pattern wastes area along walls.

What's the difference between standard PIR and dual-tech sensors?

Standard PIR detects heat changes from moving bodies. Dual-tech (PIR + microwave) requires both signals to trigger, drastically reducing false alarms from pets, heating vents, or sunlight. Dual-tech costs ~2× more but is required for high-value environments and Grade 3 (EN 50131) installations.

Where should I NOT place a PIR sensor?

Avoid placement above HVAC vents, near windows in direct sunlight, above radiators or fireplaces, and facing reflective surfaces (mirrors, polished metal). Aim the sensor across the room rather than at entry points — intruders crossing the wedge horizontally trigger the sensor more reliably than someone walking directly toward it.

Do I need a curtain PIR sensor?

Curtain PIRs project a narrow vertical 'curtain' of detection (typically 15 m × 2 m). They're ideal for windows, sliding doors, and balconies — protecting the boundary without triggering on indoor movement. Use them in addition to standard wide-angle PIRs, not as a replacement.