Compliance · US EPA
EPA Landfill Explosive Gases Control (40 CFR 258.23)
Ambient air: methane migration at municipal solid waste landfills (USA)
The US EPA's criteria for municipal solid waste landfills include an explosive gases control standard, 40 CFR 258.23. Owners and operators must ensure that the methane generated by the landfill does not exceed 25 % of the lower explosive limit (LEL) in facility structures (excluding gas control or recovery components) and does not exceed the lower explosive limit at the facility property boundary. They must run a routine methane monitoring program, at least quarterly.
Limit values
EPA 258.23 Limit Values
Every value US EPA publishes for the parameter below, with its averaging period, as the standard states it.
Who it applies to
Who Must Comply
Owners and operators of municipal solid waste landfill units in the United States, under state programs that implement Part 258. Landfill gas emissions to air are covered separately by the Clean Air Act landfill rules, whose surface emission monitoring uses a methane level of 500 ppm above background.
Monitoring
How Monitoring Demonstrates Compliance
The type and frequency of monitoring follow the site's soil, hydrogeologic, and hydraulic conditions and where its structures and boundary lie. If methane above the limits is detected, the operator must immediately protect human health and notify the State Director, record the levels and steps within seven days, and implement a remediation plan within 60 days. Continuous methane monitoring in structures and at boundary probes turns the quarterly minimum into a live warning.
Recommended
best match-
Industrial monitor for indoor and outdoor sites. Built-in sensors cover the essentials, and hot-swappable gas sensor cartridges and a differential-pressure option add more.
Gas 1
Aethair CH₄
Methane (CH₄)Molecular Property Spectrometer (MPS) MEMS sensing, poison-immune and factory-calibrated for life, for…
Also fits: Aethair MultiGas+
Gas 2
Free: one more gas sensor cartridge
MultiSense
Free: a MultiSense, stock or built to order
Expansion
Free: differential pressure
Also measures 13 more
Dew PointHeat IndexRelative HumidityIlluminance / LightParticle Count (by size)PM1PM10PM2.5Total PM / Mass Conc.Barometric PressureEquivalent Continuous Level (Leq)Sound Pressure Level (SPL)Air Temperature
Who measures each parameter
| Parameter | Aethair PRO |  Aethair IAQ |  External |
|---|---|---|---|
| Methane (CH₄) | CH₄, MultiGas+ cartridges | — | 3 instruments via Thiamis |
Devices
Devices That Cover EPA 258.23
How much of this standard one Aethair monitor covers, followed by the third-party instruments in the sensor catalog that measure its parameters. Each connects to Environet through a Thiamis gateway, which adds whatever the monitor leaves out.
Aethair monitors
Covers it on its own
Solutions
Solutions Judged Against EPA 258.23
Landfill, Biogas & Odor
Methane, H₂S, and odor complaint response
Questions
EPA 258.23 FAQ
What are the landfill methane limits under 40 CFR 258.23?
Methane may not exceed 25 % of the lower explosive limit in facility structures, or the lower explosive limit at the property boundary.
How often must landfill methane be monitored?
At least quarterly, with the type and frequency set by the site's soil and hydrogeologic conditions and the location of structures and the boundary.
What must an operator do if methane exceeds the limits?
Immediately protect human health and notify the State Director, record the levels and steps taken within seven days, and implement a remediation plan within 60 days.
Monitor Against EPA 258.23
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