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Calcimator

Chemical Exposure Assessment Calculator

Estimate airborne chemical concentration using the AIHA well-mixed room model, calculate exposure index versus OEL, and assign a risk rating.

Inputs

Results

8-hr TWA (mg/m³)

1.83

Steady-state conc. (mg/m³)2
Exposure index (C/OEL)0.04
Risk rating (1-5)1
Dose (mg/kg/day)0.13
Time to 95% C_ss (min)120
Actual Conc Mg M32
How to Use This Calculator
  1. Enter Generation rate (mg/min), Ventilation rate (m³/min), and Room volume (m³).
  2. Set Exposure duration (min), OEL (mg/m³), and Body weight (kg).
  3. Review the 8-hr TWA (mg/m³) result.
  4. Use Steady-state conc. (mg/m³) and Exposure index (C/OEL) to inform your decision.

How the result changes with Generation rate (mg/min)

Generation rate (mg/min)8-hr TWA (mg/m³)
10,0001,833.33
35,0006,416.67
65,00011,916.67
90,00016,500.01

What each input means

Generation rate (mg/min)
Contaminant generation rate in milligrams per minute from the source.
Ventilation rate (m³/min)
Total room ventilation rate in cubic metres per minute (1 cfm ≈ 0.0283 m³/min).
Room volume (m³)
Room volume in cubic metres (1 ft³ ≈ 0.0283 m³).
Exposure duration (min)
Worker exposure duration in minutes (480 min = full 8-hour shift).
OEL (mg/m³)
Occupational Exposure Limit for the chemical in mg/m³.
Body weight (kg)
Worker body weight in kilograms for dose calculation.

What each result means

Steady-state conc. (mg/m³)
Predicted steady-state airborne concentration using C = G/Q.
8-hr TWA (mg/m³)
Time-Weighted Average concentration over the 8-hour reference period.
Exposure index (C/OEL)
Ratio of TWA to OEL. Values > 1.0 indicate overexposure.
Risk rating (1-5)
1=negligible, 2=low, 3=moderate, 4=high, 5=very high.
Dose (mg/kg/day)
Estimated inhaled dose per kg body weight per day.
Time to 95% C_ss (min)
Minutes for room concentration to reach 95% of steady state.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Generation rate (mg/min) = 10, Ventilation rate (m³/min) = 5, Room volume (m³) = 200, Exposure duration (min) = 480 = 6 input(s) provided
  2. Calculate 8-hr TWA
    8-hr TWA = avgDuringExposure * min(T, 480) / 480
    1.833 = 1.833
  3. Calculate Steady-state conc.
    Steady-state conc. = generationMgMin / ventilationM3Min
    2 = 2
  4. Calculate Exposure index
    Exposure index = twa8hr / oel
    0.037 = 0.037

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