Detector Placement: Where Should Fixed Gas Sensors Be Installed?

01Let Gas Density Choose the Height

Gases stratify by vapor density relative to air. Sensors must wait for the gas at the elevation where the gas will actually arrive.

• Lighter than air (methane, hydrogen, ammonia): mount high - above leak sources, near rooflines, under canopies where pockets can accumulate
• Similar to air (carbon monoxide, nitrogen): mid-level, close to the source and breathing zone
• Heavier than air (H2S, LPG, chlorine, butane): low - near grade, in pits and trenches where heavy vapors pool, but above likely liquid accumulation points

02Start at the Leak Sources, Not the Walkways

Every valve, flange, seal, drain, and sample point is a candidate release. Detectors belong close to where gas can first escape - pumps, compressors, and fittings - with coverage built outward. Walkways and perimeters come second, as boundary monitoring, not the primary detection layer.

03Respect the Wind and the Ventilation

Air movement decides where a plume travels - and where it never arrives. Prevailing wind shifts outdoor plumes; HVAC and natural ventilation dominate indoors. A sensor downstream of the wind on the day of the leak is the one that matters.

• Use prevailing wind roses for outdoor layouts - but remember wind direction is seasonal, so coverage must work for all quadrants
• Keep detectors out of fresh-air inlets, discharge streams, and direct washdown or steam paths that dilute or flood the sample
• In enclosed spaces, place detectors where ventilation patterns carry escaping gas - and consider aspirated sampling where diffusion is too slow

04Point, Open-Path, or Ultrasonic - Match the Geometry

Not every location wants a point sensor. Long fences and perimeters favor open-path IR; outdoor turbine enclosures and vast process areas increasingly use ultrasonic leak detection that hears a release regardless of wind or dilution. Congested modules with complex geometry favor dense point coverage. The geometry of the space chooses the technology as often as the gas does.

05Don't Forget Access, Obstruction, and Maintainability

A detector behind a cable tray, inside a structural pocket, or reachable only by scaffold will drift quietly out of service. Placement must account for physical obstruction of gas flow, clearance for calibration gas access, and the realistic maintenance burden of every location you choose.