CONFINED SPACE GAS DETECTION
Calibration gas for confined space gas monitors.
A confined space gas detector is only as good as its last bump test. McNeill ships NIST-traceable calibration gas for the 4 gas monitors and single gas detectors used in confined spaces and across industry.
What a confined space 4 gas monitor checks
OSHA’s confined space standard (29 CFR 1910.146) has the atmosphere tested before entry with a calibrated direct-reading instrument: oxygen first, then flammable gases, then toxic gases. A 4 gas monitor covers all three in one unit.
- Oxygen (O₂): hazardous below 19.5% or above 23.5% by volume.
- Flammable gas (LEL): hazardous above 10% of the lower explosive limit.
- Hydrogen sulfide (H₂S) and carbon monoxide (CO): the two most common toxic gases in confined spaces.
A common 4 gas calibration mix is 25 ppm H₂S, 100 ppm CO, 2.5% methane (50% LEL) and 18% oxygen in nitrogen. Check your monitor’s calibration label for its exact values. We carry other 4 gas concentrations too.
Calibration gas by industry
The gases below are the ones detectors in each industry most often watch. The gas and concentration on your own detector’s calibration label decide what to order.
Confined space entry
Tanks, vaults, pits and silos. A 4 gas monitor checks oxygen, flammable gas (LEL), hydrogen sulfide and carbon monoxide.
4 gas mix (H₂S, CO, methane, O₂) · Trigger and fixed flow regulators
Manholes, sewers and wastewater
Hydrogen sulfide and methane build up from sewage, and oxygen can drop. Most crews carry a 4 gas monitor.
Landfills
Landfill gas monitors measure methane, carbon dioxide and oxygen in percent volume, plus hydrogen sulfide at gas wells and leachate systems.
Mining
Methane and carbon monoxide underground, plus nitrogen dioxide and nitric oxide from diesel equipment.
4 gas mix · Nitrogen dioxide · Nitric oxide · 5 gas mix with SO₂
Refineries and petrochemical
Hydrogen sulfide, hydrocarbons (often read on a pentane scale), sulfur dioxide and benzene. PID detectors for VOCs calibrate on isobutylene.
H₂S, CO, pentane mixes · Sulfur dioxide · Benzene · Isobutylene
Marine
Cargo holds, ballast tanks and engine spaces: oxygen, flammable gas, hydrogen sulfide and carbon monoxide before entry.
Fire departments and HAZMAT
4 gas monitors for overhaul and confined space rescue, plus hydrogen cyanide from burning plastics and carbon monoxide in homes.
HVAC and building services
Carbon monoxide from furnaces and boilers, natural gas and propane leaks, and carbon dioxide for indoor air quality.
Semiconductor and labs
Toxic process gases: phosphine and other hydrides, hydrogen chloride, chlorine, ammonia and hydrogen.
Phosphine · Hydrogen chloride · Chlorine · Ammonia · Hydrogen
Not sure which gas your monitor needs?
Send us the detector and sensors. We will match the gas, concentration and regulator.