How many points of gas detection do I need in a room? Where should they be placed?
These questions come up a lot in fire & gas detection system design but these seemingly simple questions do not always have easy answers.
They usually lead a series of additional questions:
- What phase is the gas in before it leaks? Is it under pressure?
- What is the temperature, both at the source of the leak and the ambient temperature?
- What’s the density of the gas – the same as air, lighter than air, or heavier than air?
- What are the regulatory (NIOSH, ISO, etc.) exposure limits?
- Could more than one gas leak at the same time?
- Where are ventilation supply and exhaust points?
The number of gas detectors and their placement depend on the type of gas, the room layout, airflow patterns, and applicable safety standards. Here’s a practical breakdown:
How Many Gas Detectors Do I Need?
There’s no single “one-size-fits-all” rule — but general guidelines are:
- Small rooms (< 250 sq ft / 25 m²): 1–2 detectors may be enough if gas release sources are few.
- Medium rooms (250–1000 sq ft / 25–100 m²): Multiple detectors are recommended, often 2–4 depending on potential leak points and ventilation.
- Large or complex spaces (> 1000 sq ft / 100 m²): A full gas detection mapping study is recommended. Detector placement should consider coverage overlap so that no “blind spots” remain.
- Many safety standards (e.g., ISA TR84.00.07, EN 60079-29-2, NFPA guidelines) recommend placing detectors based on risk analysis rather than only square footage.
Where Should Gas Detectors Be Placed?
Placement depends on the properties of the gas: 
- Lighter than air gases (e.g., hydrogen, methane, ammonia): Place detectors near the ceiling, roof, or high on walls.
- Heavier than air gases (e.g., propane, butane, CO₂, refrigerants): Place detectors near the floor, pits, or low-lying areas.
- Similar density to air (e.g., carbon monoxide): Place detectors around breathing zone height (4–6 ft / 1.2–1.8 m).
- Additional placement considerations:
- Near potential leak sources: Flanges, valves, compressors, storage tanks, gas lines.
- In corners or areas with poor ventilation: Where gases may accumulate.
- Along airflow paths: Account for HVAC, fans, or natural ventilation patterns.
- Near personnel areas: Workstations, entrances, escape routes.
Best Practices
- Use redundancy: Overlap coverage in high-risk zones.
- Follow the “5–10 meter rule”: Place detectors roughly every 5–10 m in large open areas if specific sources can’t be pinpointed.
- Test placement with smoke or tracer gas during commissioning to confirm detectors are in effective positions.
- Always align with local codes, insurance requirements, and manufacturer recommendations.
In Summary
The number and placement of gas detectors should come from a professional who will perform a risk-based assessment considering gas type, leak sources, airflow, and human occupancy .
Our expertise is in helping you answer these questions, and then selecting the gas detection equipment to meet the requirements of your application. Our partner Draeger has patented sensor technology that offers better performance, and a lower cost of ownership, compared to all other brands of gas detection.
Contact us to schedule an assessment today!