---
title: "EPA 258.23 Limits: Methane | Aethair"
description: "EPA Landfill Explosive Gases Control (40 CFR 258.23) limit values for Methane: every value and averaging period, who the standard applies to, and the…"
url: https://aethair.io/standards/epa_landfill_methane/
---

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**.

[Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure EPA 258.23 Monitoring](https://aethair.io/build/?params=ch4\&setting=outdoor)

At a glance

**US EPA** Ambient air: methane migration at municipal solid waste landfills (USA)

1 parameter · 2 limit values

[Methane (CH₄)](https://aethair.io/parameters/ch4/)

1 device measures them all

- **Aethair PRO** Aethair CH₄

[Official text from US EPA](https://www.ecfr.gov/current/title-40/chapter-I/subchapter-I/part-258/subpart-C/section-258.23)

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.

[**Methane (CH₄)** Gases & VOCs](https://aethair.io/parameters/ch4/)

**25 %LEL** *In facility structures* excluding gas control or recovery components

**100 %LEL** *At the property boundary* the lower explosive limit itself

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.

[Customize this configuration](https://aethair.io/build/?params=ch4\&setting=outdoor)

### Who measures each parameter

| Parameter | Aethair PRO | Aethair IAQ | External |
| - | - | - | - |
| [Methane (CH₄)](https://aethair.io/parameters/ch4/) | CH₄, MultiGas+ cartridges | — | [3 instruments](https://aethair.io/parameters/ch4/) 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

[**Aethair PRO** Built in + Aethair CH₄ Covers it](https://aethair.io/products/pro/)

Covers it on its own

[**TSI GM460** Gas Detectors](https://aethair.io/sensors/tsi-gas-detectors/) [**RKI Instruments GX6000** Gas Detectors](https://aethair.io/sensors/rki-instruments-gas-detectors/) [**RAE** Gas Detectors](https://aethair.io/sensors/rae-gas-detectors/)

Solutions

## Solutions Judged Against EPA 258.23

### [Landfill, Biogas & Odor](https://aethair.io/solutions/landfill-biogas/)

Methane, H₂S, and odor complaint response

[All solutions](https://aethair.io/solutions/)

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.