Chemical Exposure Limit Calculator

Compare measured concentrations against OSHA PEL, ACGIH TLV, and STEL values.

Inputs

Measured Concentration (ppm)

OSHA PEL (ppm)

ACGIH TLV-TWA (ppm)

STEL (ppm)

Exposure Duration (hours)

Tab to move between fields

Results

Adjusted TWA (ppm)

% of PEL

% of TLV60

Hazard Level (0-3)0

PEL Exceeded0

TLV Exceeded0

STEL Exceeded0

Action Level (ppm)25

Action Level Exceeded0

Safety Margin (%)70

How to Use This Calculator

Enter the Measured Concentration (ppm) from personal air sampling or direct-reading instruments.
Input the OSHA PEL, ACGIH TLV-TWA, and STEL values from the chemical's SDS or NIOSH Pocket Guide.
Set Exposure Duration (hours) to the actual time the worker was exposed during the shift (default 8 hours for a full shift).
Review the Adjusted TWA and % of PEL outputs to determine if concentrations exceed regulatory limits.
Check the Hazard Level (0–3) output: level 0 is below action, level 2 means PEL exceeded, level 3 means STEL exceeded.
Use the Safety Margin (%) result to gauge how close current conditions are to permissible limits and plan controls.

How the result changes with Measured Concentration (ppm)

Measured Concentration (ppm)	Adjusted TWA (ppm)	% of PEL
1,000	1,000	2,000
3,500	3,500	7,000
6,500	6,500	13,000
9,000	9,000	18,000

What each input means

Measured Concentration (ppm): Measured airborne concentration in ppm or mg/m³.
OSHA PEL (ppm): OSHA Permissible Exposure Limit (8-hr TWA).
ACGIH TLV-TWA (ppm): ACGIH Threshold Limit Value (8-hr TWA).
STEL (ppm): Short-Term Exposure Limit (15-minute average).
Exposure Duration (hours): Hours of exposure during the shift.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Measured Concentration (ppm) = 15, OSHA PEL (ppm) = 50, ACGIH TLV-TWA (ppm) = 25, STEL (ppm) = 75 = 5 input(s) provided
Calculate Adjusted TWA
Adjusted TWA
15 = 15
Calculate % of PEL
% of PEL
30 = 30
Calculate % of TLV
% of TLV
60 = 60
Calculate Hazard Level
Hazard Level
0 = 0

Engine last updated July 28, 2026. Checked against 2 independently-derived tests — how we verify calculators.

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

OSHA & Workplace Safety

Confined Space Air Monitoring Calculator

Evaluate LEL, O2, H2S, and CO readings against OSHA action levels for permit-required confined spaces.

HAZMAT

Air Monitoring Action Levels Calculator

Interpret PID/FID readings against site-specific action levels and determine PPE protection level.

Industrial Hygiene

PEL Compliance Calculator

Calculate Time-Weighted Average (TWA) exposure and compare against the OSHA Permissible Exposure Limit to assess compliance.

Air Quality

Ventilation Dilution Calculator

Calculate required dilution ventilation to control airborne contaminants below TLV/PEL limits.

Acoustics

Sound Masking Calculator

Calculate OSHA noise dose and time-weighted average (TWA) from multiple exposure periods. Determines compliance with OSHA PEL (90 dBA / 8 hr) using the 5 dB exchange rate.