Industrial Hygiene Calculators — 13 Free Tools

Q: Why don't you pre-fill OELs, TLVs, or PELs?

Three reasons: the ACGIH TLV booklet is copyrighted, regulatory values change yearly so a hardcoded value would become stale, and using your own source ensures traceability of your assessment.

What this section is about

This section groups calculation tools useful for industrial hygiene practice in Quebec and elsewhere. Specialized unit conversions, time-weighted averages, ventilation, noise, heat stress, exposure statistics. Each tool applies a recognized formula. Sources are cited at the bottom of every tool.

We do not pre-fill regulatory values (OELs, TLVs, PELs), you enter the value applicable to your situation, which avoids licensing issues and ensures you work with the current version of the relevant reference. Everything runs in your browser; no data is sent to any server.

These calculators do the math. They don't do the thinking. Use them to check a number, sketch a scenario, or sanity-test a vendor claim, but the call about whether your workplace is actually safe still belongs to a certified industrial hygienist who knows the substance, the worker, and the room.

Conversions and units

ppm ↔ mg/m³ Converter — Convert atmospheric contaminants between ppm and mg/m³ at any T and P.
Industrial Hygiene Units Converter — Pressure, flow, velocity, and aerosol concentrations — beyond a generic unit converter.

Exposure assessment

TWA Calculator — Time-weighted average exposure across multiple samples.
STEL / Excursion Checker — Verify peaks against STEL or the ACGIH 3× / 5× excursion rule.

Industrial ventilation

Flow Rate Calculator (Q = V × A) — Volumetric airflow from velocity and section. Round, rectangular, or direct area.
Air Changes per Hour (ACH) — Room ventilation rate, or required airflow for a target ACH.
Velocity Pressure ↔ Air Velocity — Pitot-tube physics with optional density correction.

Noise

Noise Level Addition — Combine multiple sound sources logarithmically.
Noise Distance Attenuation — Sound level vs distance for point or line sources in free field.
Noise Dose & TWA — Cumulative dose using NIOSH, OSHA, or Quebec criteria.
Hearing Protector Effectiveness (NRR) — Effective NRR via the CCOHS / CSA Z94.2 derating method.

Physical agents

WBGT Calculator (Heat Stress) — Wet-bulb globe temperature for indoor or outdoor environments.
Inverse Square Law — Intensity vs distance for point-source radiation in free space.

Frequently asked questions

Why don't you pre-fill OELs, TLVs, or PELs?

Three reasons. The ACGIH TLV booklet is copyrighted. Regulatory values change yearly — a hardcoded value would become stale. And using your own source ensures traceability of your assessment.

Is my data sent to a server?

No. All calculations run in your browser. No data is transmitted. You can use the tools offline after first page load.

Can I use these tools in a professional report?

Yes, as long as you cite the formula sources and sign the report under your own professional responsibility. These tools do not replace your professional judgment or your professional body's obligations.

Are the formulas validated?

Formulas come from recognized sources (ACGIH, NIOSH, OSHA, IRSST, ASHRAE, CCOHS, CSA) cited in each tool. The author makes no guarantee on the implementations. For critical use, cross-check with an independent calculation.

Which jurisdictions do these tools cover?

Formulas are jurisdiction-neutral. Cited references mainly cover Quebec (RSST, IRSST, CCOHS), North America (ACGIH, NIOSH, OSHA, ASHRAE, CSA), and some international standards (ISO 7243, ISO 9613). You must ensure the formula and reference chosen match your jurisdiction.

By Bam's Thinkery — Updated May 2, 2026