Methane (CH₄)

CAS Number: 74-82-8
Methane (CH₄) is a colorless, odorless, highly flammable gas that is the primary component of natural gas. It is a simple asphyxiant — not toxic in itself, but dangerous because it displaces oxygen in enclosed spaces. Methane is the leading cause of explosive atmospheres in coal mines, landfills, sewers, agricultural biogas facilities, and natural gas infrastructure. The gas has a flammable range of 5–15% in air (LEL 5%, UEL 15%). Its presence is typically detected using LEL/combustible gas sensors. Methane is also a potent greenhouse gas and its monitoring is increasingly important for environmental compliance and emissions reporting.

Methane (CH₄) is a colorless, odorless flammable gas and the primary component of natural gas. Rent methane detection equipment from RAECO Rents to support confined space entry, landfill monitoring, and natural gas leak investigations where combustible gas buildup is a concern. All rental instruments are bump tested before each rental so crews can confirm sensor response before heading into the field.

Regulatory Exposure Limits

Updated on March 09, 2026

OSHA PEL
TWA: No established PEL
STEL: N/A
C: N/A
NIOSH REL
TWA: No established REL
STEL: N/A
C: N/A
ACGIH TLV
TWA: No established TLV
STEL: N/A
C: N/A
Frequently Asked Questions
Common questions about
Do I need a standard 4-gas monitor for methane work?
A standard 4-gas monitor includes an LEL sensor that will detect methane, but if methane detection and flammability assessment is your primary need, you may want a dedicated methane-specific instrument or one calibrated specifically for methane rather than a methane-equivalent LEL sensor. For confined space entry where methane may be present alongside H₂S, CO, and O₂ deficiency, the standard 4-gas is the right tool.
What should I know before renting methane monitoring for landfill or excavation work?
Confirm whether you need surface screening, subsurface checks, or confined space entry monitoring; whether you need data logging for reports; and what other gases might be present. Those details drive whether you need basic LEL monitoring or a more specialized setup.
Is methane on this job an explosion risk, an asphyxiation risk, or both?
It's an explosion risk when methane can reach flammable concentrations near ignition sources—common in confined spaces and utility work. It's an asphyxiation risk when methane displaces oxygen in enclosed spaces, even if it's not near the flammability range. In practice, you manage both by monitoring LEL and oxygen together.
Why can methane readings create false confidence?
Relying on odor, skipping bump tests, assuming the opening measurement represents the whole space, and not monitoring oxygen alongside LEL. Methane monitoring is most reliable when it's part of a consistent confined-space testing routine.
Where should I test to avoid missing methane buildup?
Test at multiple levels and deeper into the space—not just at the opening. Methane is lighter than air, but airflow patterns and stratification can still create pockets. A pump-driven sample is often helpful when you can't safely access where the gas may accumulate.
Do I need a methane spot check or continuous monitor?
Spot checks tell you conditions at a moment; continuous monitoring tells you whether conditions stay acceptable while work is happening—especially when ventilation cycles, products release, or work activities change. For confined space entry, continuous monitoring is typically the safer standard.
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