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Short Term Exposure Limit Calculator

Work out short term exposure limit instantly with clear inputs, formula shown and shareable results.

About Short Term Exposure Limit Calculator

A short term exposure limit is a fifteen minute time weighted average that must not be exceeded at any point in the shift, even where the eight hour average is compliant. Conventional practice also limits excursions to four per shift, each no longer than fifteen minutes and separated by at least sixty minutes.

Formulas

STEL check

Ratio = peak fifteen minute concentration / STEL

Excursion rule

No more than four excursions of 15 minutes each, at least 60 minutes apart

Worked example

With the default values below, Short Term Exposure Limit Calculator returns Peak as share of the STEL of 120.00%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Peak concentration measuredminimum 0 ppm
120 ppm
Short term exposure limitminimum 0.001 ppm
100 ppm
Duration of the peakminimum 1 min
15 min
Excursions per shiftminimum 1
2

Results

Peak as share of the STEL
120.00% %
Total time at peak
30 min
Excursion frequency check
Within the usual excursion rules
Assessment
STEL exceeded — immediate control required

Step by step

  1. 1Values used
  2. 2STEL check
  3. 3Excursion rule
  4. 4Peak as share of the STEL= 120.00 %
  5. 5Total time at peak= 30 min
  6. 6Excursion frequency check= Within the usual excursion rules
  7. 7Assessment= STEL exceeded — immediate control required

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Short term limits and excursion rules must be taken from the exposure limit list adopted by your regulator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Short term limits and excursion rules must be taken from the exposure limit list adopted by your regulator.

Frequently Asked Questions

How is the Short Term Exposure Limit figure worked out?

Ratio = peak fifteen minute concentration / STEL. A short term exposure limit is a fifteen minute time weighted average that must not be exceeded at any point in the shift, even where the eight hour average is compliant.

What if a substance has no STEL?

The excursion limit applies instead: exposure should not exceed three times the eight hour limit for more than thirty minutes, and never five times the limit.

What values do I need to enter?

This calculator takes 4 inputs: Peak concentration measured, Short term exposure limit, Duration of the peak, Excursions per shift. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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