40 records

What assigned protection factor does this respirator have?

40 records covering 6 respirator types, one fact each. Every value is transcribed from the source that states it and carries the sentence it was taken from: 2 sources across 2 sites, last checked 2026-09-24, due for re-check by 2028-09-23. Every record is listed below, each linking the page its value came from.

Cite as: Respirator assigned protection factors — federal OSHA and Cal/OSHA, with maximum use concentrations, referencesource.org/respirator-assigned-protection-factors/, checked 2026-09-24.

About this data

Assigned protection factors (APFs) for each respirator class under federal OSHA (29 CFR 1910.134 Table 1) and Cal/OSHA (8 CCR 5144), and — the derived layer — the maximum use concentration (MUC) each respirator class supports for a given substance, computed as APF × the applicable exposure limit. The regulation itself states the formula ('The MUC can be determined mathematically by multiplying the assigned protection factor... by the required OSHA permissible exposure limit'), but nobody publishes the computed per-substance table, and OSHA and Cal/OSHA limits differ up to 10× for 66 substances — so the same respirator is adequate federally and inadequate in California for the same job. Answers 'what APF does a half mask have', 'what respirator do I need for styrene at 300 ppm', and 'is my respirator sufficient under Cal/OSHA'. Pairs with the existing workplace-exposure-limits asset (1,184 records, two authorities) — the MUC pages are that asset multiplied through this one.

The data

Where this came from

Every record above links the page it was taken from and quotes the sentence that states it. These are the 2 sources this dataset was assembled from.

• ecfr.govhttps://www.ecfr.gov/current/title-29/subtitle-B/chapter-XVII/part-1910/subpart-I/section-1910.134
• dir.ca.govhttps://www.dir.ca.gov/title8/5144.html

Machine-readable

• data.jsonThe whole dataset — every record with its source URL and source quote.
• Open Knowledge Format bundleOne JSON object per line — every record's frontmatter and quoted span exactly as it is held here, in one fetch.
• data.csvThe same records as one flat table, for a spreadsheet or a dataframe. The last four columns are the source URL, the quoted sentence it was read from, the date we last checked it, and which columns are our reading rather than the page's words.
• How this is made and checkedWhat "verified against source" does and does not mean.

From your own code

Same records, same quotes, without scraping the page: refsource is on PyPI and npm. Each value comes back carrying the URL it was read from and the sentence on that page that states it — .source and .quote sit on the value itself rather than in a side channel, so the checking step is available instead of skipped.

pip install refsource
refsource lookup respirator-assigned-protection-factors respirator_class="Air-Purifying Respirator"

npx -y refsource lookup respirator-assigned-protection-factors respirator_class="Air-Purifying Respirator"

Set your AI assistant up to use this

Two files and no account. Put this in .mcp.json at the root of your project — Claude Code, Cursor, Windsurf, VS Code and Codex all read that file — and your assistant can look this dataset up instead of recalling it. The server is remote, keyless and read-only.

{
  "mcpServers": {
    "referencesource": {
      "type": "http",
      "url": "https://referencesource.org/mcp"
    }
  }
}

Add to Cursor · or, on the command line: claude mcp add --transport http referencesource https://referencesource.org/mcp --scope project

Then one line in the project's CLAUDE.md or AGENTS.md, so the assistant knows when to reach for it:

When a question needs "Respirator assigned protection factors — federal OSHA and Cal/OSHA, with maximum use concentrations", call the referencesource MCP server at https://referencesource.org/mcp (tool `search_records`, dataset_slug `respirator-assigned-protection-factors`) instead of answering from memory — every record it returns carries its source URL and a verbatim quote from that page.

What each tool does, and the servers built over single registers: Connect your AI assistant.

40 records. last verified against source 2026-09-24. due for re-check by 2028-09-23.

Licence. US federal and California regulatory text; facts not copyrightable, sections quoted with citation.