FIX800 Hazardous Gas Monitoring in Underground Utility Rooms — Wastewater Room, Machine Room, Boiler Room, Electrical Room

This article presents installation cases for the most frequently requested application type in recent months. In buildings, factories, and large facilities, underground spaces typically house electrical rooms, boiler rooms, wastewater treatment rooms, and fire suppression agent rooms. Because these spaces are below grade, natural ventilation through windows is not possible without mechanical air handling systems—which is why they are designated as confined spaces.

Why Each Room Type Requires Gas Monitoring

Electrical rooms distribute high-voltage power; short circuits and overloads create serious fire risk → managed with CO and LEL sensors.

Boiler rooms risk incomplete combustion when flue gas backdrafts or oxygen supply is insufficient, leading to fire and asphyxiation hazards → managed with CO, O₂, and LEL sensors.

Wastewater treatment rooms / septic tanks generate toxic gases from sludge; backflow can cause fatal asphyxiation → managed with O₂, H₂S, and LEL (NH₃) sensors.

Fire suppression agent rooms storing CO₂, refrigerant, or halon pose asphyxiation risk if agents discharge or leak accidentally → managed with O₂ and CO₂ sensors.

By monitoring the appropriate gases in each room type, it is possible to prevent asphyxiation fatalities, gas leaks, and explosion incidents in these confined spaces.

This project involved installing a gas concentration monitoring system in the underground confined-space utility rooms—including the electrical room and boiler room—of a large shopping mall.

Installation Safety

Safety is the first and foremost priority. Scaffold platforms are used wherever possible for elevated work, and ladder use requires a two-person team as a mandatory requirement.

Sensor Placement Relative to Gas Density

At this site, the safety manager specifically requested that detector placement take gas density into account. Regarding gas density and mounting height, the recommended approach is:

"While guidelines recommend considering gas density when positioning detectors, installing a sensor near the most likely leak source is far more important than mounting height alone. For example, if a 1 m-tall CO₂ cylinder is present, the standard guidance suggests mounting 30 cm above the floor because CO₂ is heavier than air—but it is more effective to mount the sensor near the cylinder valve. Gas does not immediately descend upon release; early detection depends on proximity to the leak point."

Conduit material was matched to the existing cable management on site. GW flexible, flame-retardant, steel, and explosion-proof conduit types are selected in advance through site consultation and installed accordingly.

Taking both the wide distribution of potential leak points and the site safety manager's specific request into account, the following mounting positions were applied:

1. Carbon monoxide (CO, density similar to air) and oxygen (O₂) — mounted at breathing height
2. Methane / LEL (lighter than air) — mounted above head height
3. Hydrogen sulfide (H₂S, heavier than air) — mounted near floor level

Dual Monitoring: Interior and Entrance

A gas concentration display panel was installed at the entrance to the confined space, enabling dual-point management of internal gas levels from both inside and at the entry point. In spaces such as fire suppression agent rooms where high concentrations of gas are stored, a worker entering during a leak event may lose consciousness immediately. Dual-location monitoring is considered essential in such environments.

Many first-time enquirers are concerned that selecting and installing gas detectors will require a large budget or involve complex, hazardous work. In practice, gas detector installations use surface-run conduit and are straightforward to execute. Workplace safety gas detectors are also among the more affordable categories of gas measurement equipment.