Types of Occupancy Sensors: What They Are and How They Differ

Occupancy sensors commonly include passive infrared (PIR), ultrasonic, microwave (including mmWave radar), camera/computer-vision, thermal imaging, acoustic/audio, environmental (CO2/VOC), RF/Bluetooth/Wi‑Fi presence, RFID/badge-based, pressure/contact, doorway beam-break/people-counting, and hybrid dual-technology devices; each detects presence in a different way and suits different spaces and privacy needs. These sensors underpin lighting controls, HVAC optimization, and space analytics, and choosing the right type depends on motion patterns, room layout, ceiling height, privacy, code compliance, and integration requirements.

Core Sensing Technologies

The technologies below represent the primary ways occupancy can be detected, from motion and heat to signals emitted by devices people carry. Each has distinct strengths, weaknesses, and ideal use cases.

• Passive Infrared (PIR): Detects changes in heat (infrared) from moving bodies crossing zones. Best for line-of-sight, low-cost, low-power lighting control.
• Ultrasonic: Emits inaudible sound waves and senses frequency shifts from movement. Good for covered or partitioned areas; can be more sensitive to minor motion; susceptible to air currents and HVAC noise if not tuned.
• Microwave (Doppler radar): Uses radio waves to detect motion through frequency shift; penetrates certain materials, covers larger areas; can cause false triggers beyond room if not contained. Includes modern mmWave (e.g., 60 GHz FMCW) for fine-grained presence (e.g., seated, micro-motions).
• Camera/Computer Vision (RGB/Depth/AI): Identifies people and counts them; can estimate dwell time and direction. Rich analytics but heightened privacy and cybersecurity requirements; many systems now run edge-AI with on-device processing and privacy filters.
• Thermal Imaging (Infrared Array): Detects heat signatures without capturing identifiable images; better privacy than RGB cameras, useful in low light and through some visual obstructions.
• Time-of-Flight/3D (LiDAR or depth sensors): Measures distance to objects to detect presence and count people with high accuracy; typically more costly but precise for flow and zoning.
• Acoustic/Audio: Uses sound signatures or simple noise thresholds to infer occupancy; low-cost but can be less precise and raises privacy considerations if raw audio is retained.
• Environmental Proxies (CO2/VOC/Humidity/Temp): Infers presence from rising CO2 or humidity; good for HVAC demand control ventilation; slower response and less precise for immediate lighting control.
• RF/Bluetooth/Wi‑Fi Presence: Detects smartphones or beacons to infer occupancy or identify users; supports wayfinding and hot-desking; depends on users carrying enabled devices and consent.
• RFID/Badging/Access Control: Uses card swipes or UWB tags to register entries/exits; high confidence at portals, limited within-room granularity unless combined with other sensors.
• Pressure/Contact (Mats, Chair Sensors, Desk Pads): Direct detection of seated or standing presence; excellent for workstations and vehicles; requires per-point installation and maintenance.
• Doorway Beam-Break/People Counters: Infrared beams or stereo sensors at entrances to tally in/out; reliable counting for rooms and retail; needs drift correction and clear doorways.
• Dual-Technology/Hybrid: Combines methods (e.g., PIR + ultrasonic, PIR + microwave, thermal + vision) to reduce false triggers and improve hold-on with minor motion.

Together, these options span instant motion detection, persistent presence sensing, and analytics-grade counting. Hybrids often deliver the best reliability by balancing sensitivity with false-alarm immunity.

Form Factors and Mounting Styles

How a sensor is packaged and installed affects coverage, aesthetics, and maintenance. Common form factors suit specific ceiling heights, room sizes, and retrofit constraints.

• Wall-switch sensors: Replace standard switches; ideal for small rooms and retrofits; mostly PIR or dual-tech.
• Ceiling-mount (low/high-bay): Broad, symmetrical coverage; high-bay versions suit warehouses and gyms; often PIR, ultrasonic, microwave, or mmWave.
• Corner/wall-mount: Targets corridors and perimeter zones; helps avoid spill-over into adjacent rooms.
• In-fixture or sensor-ready luminaires: Embedded sensors per fixture for granular control and data.
• PoE and IoT nodes: Networked ceiling sensors powered via Ethernet for data-rich analytics and BMS integration.
• Battery-powered wireless: Fast installation; typical in retrofits; uses Zigbee, Thread, BLE Mesh, Z‑Wave, or proprietary protocols.
• Door-frame/entrance counters: Focused people counting at portals for accurate room-level occupancy.

Mounting choice often determines reliability and cost-to-install; ceiling sensors usually provide the most uniform coverage, while wall-switch units are the quickest retrofit for code compliance.

Control Modes and Integration

Beyond sensing, the control logic and network interface shape user experience, energy savings, and interoperability with lighting and HVAC systems.

• Occupancy mode (auto-on/auto-off): Lights/HVAC turn on when occupancy is detected and off after a timeout.
• Vacancy mode (manual-on/auto-off): Requires manual-on to reduce nuisance-ons; often mandated by energy codes in some spaces.
• Partial-on/partial-off: Limits auto-on levels (e.g., 50%) to save energy and reduce glare; completes off automatically.
• Presence vs. motion detection: mmWave radar and pressure sensors sustain “presence” without visible motion, improving user comfort.
• Integration protocols: Analog 0–10 V, DALI-2, BACnet/IP, Modbus, KNX, N2, plus wireless Zigbee, Thread/Matter, BLE Mesh, Z‑Wave, Wi‑Fi, EnOcean, and PoE/IP for enterprise platforms.
• Tuning parameters: Sensitivity, time delay, walk-through mode, daylight hold-off, and hold times to match space behavior.

Well-integrated systems pair the right sensor with appropriate control logic, minimizing false triggers while ensuring comfort and compliance.

Selection Criteria and Best-Fit Use Cases

Choosing the right sensor starts with the space’s motion patterns, desired responsiveness, and privacy expectations, then narrows by installation practicalities and codes.

• Space type/motion profile: Offices (mmWave/PIR), restrooms (dual-tech), open offices (ceiling PIR or radar), classrooms (dual-tech), warehouses (high-bay PIR/microwave), conference rooms (counting/CO2).
• Privacy requirements: Prefer thermal, mmWave, or PIR over cameras in sensitive areas; ensure edge processing if using vision.
• Ceiling height and geometry: High ceilings favor microwave or high-bay PIR; partitions benefit from ultrasonic or radar.
• False-trigger risk: Nearby corridors or HVAC movement can trip ultrasonic/microwave; aim zones carefully and adjust sensitivity.
• Energy codes: Align with ASHRAE 90.1/IEC/IECC and local amendments (e.g., vacancy or partial-on requirements).
• Power/wiring: Decide between line-voltage, low-voltage, PoE, or battery-powered wireless based on retrofit complexity.
• Cybersecurity/data governance: Especially for camera/Wi‑Fi/BLE-based systems; enforce encryption and data minimization.
• Maintenance: Battery life and access for replacements; calibration needs for ultrasonic/microwave.
• Analytics needs: People counts and utilization heatmaps require camera, depth, LiDAR, or calibrated counters.
• Budget: PIR is most economical; mmWave and vision/depth cost more but offer superior presence fidelity and insights.

A clear requirements matrix—space type, privacy, integration, and budget—usually reveals one or two optimal technologies, often in hybrid combination.

Common Combinations

Pairing sensors reduces missed detections and nuisance activations by leveraging complementary strengths.

• PIR + Ultrasonic: Widely used in classrooms and offices; PIR confirms line-of-sight motion, ultrasonic maintains presence behind partitions.
• PIR + Microwave: Extends range in large or high spaces; requires careful aiming to avoid adjacent-room triggers.
• Thermal + Vision (edge AI): Enhances counting accuracy while protecting identities via thermal checks and on-device processing.
• People counter + Door contact: Improves in/out accuracy and drift correction at room portals.

Dual-technology devices typically default to conservative “on” rules and stricter “off” rules, balancing comfort and energy savings.

Emerging Trends (2024–2025)

Recent advances improve accuracy, privacy, and interoperability, especially for hybrid work and smart building platforms.

• mmWave radar-on-chip (60–77 GHz): Detects micro-movements for seated presence and bed/chair occupancy; increasingly common in offices and vehicles.
• Edge AI with privacy-by-design: On-device inference, face blurring, and metadata-only outputs to meet GDPR and enterprise policies.
• Battery-free/energy-harvesting sensors: EnOcean and solar/thermal scavenging reduce maintenance for dense deployments.
• Thread/Matter and IP convergence: Easier integration with consumer and commercial ecosystems while bridging to BACnet/enterprise BMS.
• Multi-sensor ceiling tiles: Unified nodes combining PIR/mmWave, acoustics, CO2, and light for holistic control and analytics.
• UWB and BLE RTLS: High-precision indoor location for asset tracking and optional presence in high-value areas.

The net effect is more reliable presence detection with less intrusive data collection and smoother integration into building platforms.

Summary

Occupancy sensors span PIR, ultrasonic, microwave/mmWave, camera/vision, thermal, acoustic, environmental, RF/BLE/Wi‑Fi presence, RFID/badging, pressure/contact, doorway counters, and hybrids. Select based on space behavior, privacy, ceiling height, wiring, code compliance, and integration. For most commercial interiors, ceiling-mounted PIR or dual-tech (PIR + ultrasonic or mmWave) offers a robust baseline; analytics-heavy or high-accuracy counting calls for vision/depth or portal counters, and HVAC load control often benefits from CO2-based inference. Thoughtful pairing and tuning deliver the best balance of user comfort, energy savings, and data value.

What are the options for occupancy sensors?

We offer PIR sensors with XCT technology, as well as dual-technology (PIR and ultrasonic) sensors with XCT technology. An occupancy sensor automatically turns lights on when you enter a room and off when you leave, making this type of sensor the most convenient, since you never have to touch the lighting controls.

What are the three types of occupant detection systems?

Comparison of Key Occupancy Sensing Technologies

Technology	Common Applications
PIR (Passive Infrared)	Offices, Workstations Restrooms, Libraries
Ultrasonic Occupancy Sensors	Restrooms, Libraries, Hospital Patient Rooms
Microwave Occupancy Sensors	Parking Lots and Garages, Warehouses, Outdoor Security

What are the two common types of occupancy sensors?

There are many different types of occupancy sensors, including Passive Infrared (PIR), Ultrasonic, Bluetooth Beacons, and Optical sensors. Each utilizes a different kind of technology to make sense of its surroundings.

What are the four main types of sensors?

In general, we can classify sensors into four types:

• Active Sensors. Active sensors require an external power source to function.
• Passive Sensors. According to a study, passive sensors generate their own electric signal.
• Analog Sensors. Analog sensors produce a continuous output signal or measurement.
• Digital Sensors.