About this tool

Why it exists

Selecting respiratory protection means turning an exposure measurement into a decision: which respirators are adequate, and up to what concentration. The underlying method — hazard ratio, assigned protection factor, and maximum use concentration — is well defined by OSHA, but it is usually buried in guidance PDFs or worked out by hand on a whiteboard. This tool does that arithmetic instantly, shows its work, and cites its sources.

How the data is maintained

The assigned protection factors come directly from OSHA 29 CFR 1910.134, Table 1 — public federal regulation. IDLH values come from NIOSH, and permissible exposure limits from OSHA. Every dataset carries a source and a “last verified” date, and is re-checked periodically because standards change. We deliberately do not bundle copyrighted values such as ACGIH TLVs; you enter your own exposure limit instead.

Principles

• Accuracy first. The value of a reference tool is being right. Numbers are traceable to their source.
• Transparent. The method and the full APF table are published on the how it works page.
• Private and fast. All calculations run in your browser. Nothing you type is uploaded.
• Reference, not advice. The tool supports professional judgment; it does not replace it.

Who maintains this

This tool is built and maintained by Hemant Rawat, a software and machine-learning engineer who builds fast, accurately-sourced reference tools. Every value is cited directly from OSHA and NIOSH primary sources and is re-checked periodically against them.

In the interest of transparency: this content is not yet authored or reviewed by a Certified Industrial Hygienist (CIH). Independent professional review is planned, and this page will name the reviewer once that is in place. Until then, please treat the calculator as a reference and verify results with a qualified professional.

Independence

This site is an independent educational resource. It is not affiliated with, endorsed by, or sponsored by OSHA, NIOSH, or any respirator manufacturer. Product categories are generic regulatory classes, not specific brands.

Questions or corrections are welcome — please get in touch.