---
title: "MSHA Silica Limits: Respirable Crystalline Silica | Aethair"
description: "MSHA Respirable Crystalline Silica (30 CFR Part 60) limit values for Respirable Crystalline Silica: every value and averaging period, who the standard…"
url: https://aethair.io/standards/msha_silica/
---

Compliance · US MSHA

# MSHA Respirable Crystalline Silica (30 CFR Part 60)

Occupational: mines (USA)

The US Mine Safety and Health Administration's respirable crystalline silica rule, **30 CFR Part 60** (2024), sets the limit for miners: a **permissible exposure limit of 50 µg/m³** for a full shift, calculated as an 8-hour time-weighted average, and an **action level of 25 µg/m³** that sets how often exposure must be sampled. It brings mines in line with the limit OSHA set for other industries in 2016.

[Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Configure MSHA silica Monitoring](https://aethair.io/build/?params=silica)

At a glance

**US MSHA** Occupational: mines (USA)

1 parameter · 2 limit values

[Respirable Crystalline Silica](https://aethair.io/parameters/silica/)

1 device measures them all

- **Thiamis** Trolex Particulate & Dust Monitors

[Official text from US MSHA](https://www.ecfr.gov/current/title-30/chapter-I/subchapter-M/part-60)

Limit values

## MSHA silica Limit Values

Every value US MSHA publishes for the parameter below, with its averaging period, as the standard states it.

[**Respirable Crystalline Silica** Particulate Matter](https://aethair.io/parameters/silica/)

**50 µg/m³** *8-hour TWA (PEL)* full shift

**25 µg/m³** *8-hour TWA (action level)* full shift

Who it applies to

## Who Must Comply

Operators of US mines. The compliance date was **April 14, 2025 for coal mines** and **April 8, 2026 for metal and nonmetal mines**.

Monitoring

## How Monitoring Demonstrates Compliance

Compliance rests on full-shift sampling of each miner who may be exposed, with a respirable sampler analyzed for crystalline silica. Below the action level, a second sample is taken within three months; at or above it, sampling continues every three months; above the PEL, the operator takes corrective action and samples again. Real-time respirable dust monitoring shows which tasks and places generate dust and whether controls such as cab filtration are working, between those samples.

[Customize this configuration](https://aethair.io/build/?params=silica)

### Who measures each parameter

| Parameter | Aethair PRO | Aethair IAQ | External |
| - | - | - | - |
| [Respirable Crystalline Silica](https://aethair.io/parameters/silica/) | — | — | [1 instrument](https://aethair.io/parameters/silica/) via Thiamis |

Devices

## Devices That Cover MSHA silica

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.

Covers it on its own

[**Trolex** Particulate & Dust Monitors](https://aethair.io/sensors/trolex-particulate-dust-monitors/)

Solutions

## Solutions Judged Against MSHA silica

### [Cabin Air Quality](https://aethair.io/solutions/cabin-air/)

Respirable dust, gases, and blast monitoring

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

Questions

## MSHA silica FAQ

What is the MSHA silica limit?

50 µg/m³ of respirable crystalline silica for a full shift, calculated as an 8-hour time-weighted average, with an action level of 25 µg/m³.

When did the MSHA silica rule take effect?

April 14, 2025 for coal mines and April 8, 2026 for metal and nonmetal mines.

Does a real-time dust monitor satisfy the MSHA rule?

No. Compliance rests on full-shift sampling analyzed for crystalline silica; real-time monitoring helps control dust between samples.