Calculator overview

Inputs and outputs

This summary comes from the calculator's published input and output contract.

Inputs

WBG Unit System: About this input

Unit used for every temperature, threshold, and adjustment. Changing this selector does not convert entered values.

Default Celsius Allowed Celsius, Fahrenheit
WBG Exposure Mode: About this input

Select the significant-radiant-load equation for direct sun or meaningful industrial radiant heat; otherwise select no significant radiant load.

Default No significant radiant load Allowed No significant radiant load, Significant radiant load (solar or industrial)
WBG Natural Wet Bulb: About this input

Natural, unaspirated wet-bulb sensor reading; do not substitute an ordinary psychrometric wet-bulb value.

Unit °C Default 25 Range -100 to 250
WBG Globe Temperature: About this input

Black-globe sensor reading representing radiant heat at the work location.

Unit °C Default 30 Range -100 to 250
WBG Dry Bulb Temperature Conditional: About this input

Ambient dry-bulb sensor reading. Visible and required only for the significant-radiant-load equation.

Unit °C Default 32 Range -100 to 250
WBG Clothing Adjustment: About this input

User-entered, site-approved adjustment added to measured WBGT. No clothing table is embedded.

Unit °C difference Default 0 Range 0 to 50
WBG Action Threshold: About this input

User-entered lower decision threshold. The default is illustrative only and must be replaced with approved site guidance.

Unit °C Default 27 Range -100 to 250
WBG Limit Threshold: About this input

User-entered upper decision threshold. It must be greater than the action threshold.

Unit °C Default 30 Range -100 to 250

Outputs

WBG Measured WBGT Conditional: About this output

Measured-sensor WBGT before clothing adjustment.

Unit °C
WBG Effective WBGT Conditional: About this output

Measured WBGT plus the user-entered clothing adjustment.

Unit °C
WBG Action Margin Conditional: About this output

Action threshold minus effective WBGT. Positive is below the threshold; zero or negative has reached it.

Unit °C difference
WBG Limit Margin Conditional: About this output

Limit threshold minus effective WBGT. Positive is below the threshold; zero or negative has reached it.

Unit °C difference
WBG Natural Wet Bulb Contribution Conditional: About this output

The numeric 0.7*Tnwb term. In Fahrenheit it is not a standalone absolute temperature; only the full weighted sum has temperature meaning.

Unit weighted numeric term
WBG Globe Contribution Conditional: About this output

The numeric 0.3*Tg no-radiant or 0.2*Tg significant-radiant term; it is not a standalone absolute temperature in Fahrenheit.

Unit weighted numeric term
WBG Dry Bulb Contribution Conditional: About this output

The numeric 0.1*Tdb term used only in significant-radiant mode; it is not a standalone absolute temperature in Fahrenheit.

Unit weighted numeric term
WBG Threshold Band: About this output

Generic comparison with the user-entered thresholds; it is not a declaration of safety.

No unit declared
WBG Formula Used: About this output

Makes the active equation explicit.

No unit declared
Model Status: About this output

Returns an actionable NOT VALID or CHECK reason for invalid inputs or a reached user threshold; otherwise OK.

No unit declared

Methodology

Purpose and model boundary

This model calculates measured and clothing-adjusted Wet Bulb Globe Temperature (WBGT) from user-entered instrument readings, then compares the result with site-approved action and limit thresholds. It is a measured-sensor calculator, not a weather-to-WBGT estimator, and it does not determine by itself whether work is safe.

Inputs and units

The unit selector applies to every sensor reading, threshold, and clothing adjustment. Changing it does not convert entered values, so the numbers must already use the selected Celsius or Fahrenheit basis consistently. The exposure mode selects whether dry-bulb temperature participates. Natural wet-bulb and globe readings are always required; dry bulb is required only for significant solar or industrial radiant load. The clothing adjustment is entered as a temperature difference and added to measured WBGT.

Governing relationships

For no significant radiant load:

WBGT_measured = 0.7 × T_nwb + 0.3 × T_g

For significant radiant load:

WBGT_measured = 0.7 × T_nwb + 0.2 × T_g + 0.1 × T_db

The effective value and threshold margins are:

WBGT_effective = WBGT_measured + clothing adjustment

action margin = action threshold - WBGT_effective

limit margin = limit threshold - WBGT_effective

A positive margin is below the threshold; zero or negative means it has been reached. In Fahrenheit mode, the individual weighted contribution terms are numeric components of the complete affine weighted sum and should not be interpreted as standalone absolute temperatures.

Calculation sequence

Validate unit and exposure selections, active sensor readings, clothing adjustment, and ordered thresholds.
Use the two-sensor or three-sensor equation according to radiant-load mode.
Add the clothing adjustment to obtain effective WBGT.
Calculate action and limit margins, threshold band, and the clothing-adjustment sensitivity chart.
Evaluate the workbook status in the precedence below.

Outputs and interpretation

Measured WBGT is the instrument-equation result before clothing. Effective WBGT is the value compared with user-entered thresholds. The workbook exposes weighted sensor contributions to make the active equation auditable, plus a text description of the formula used. The thresholds must already reflect the site's workload, acclimatization, clothing, exposure-duration, and applicable-guidance decisions.

Validation and status logic

Condition, evaluated in order	Returned status
A unit, exposure mode, active sensor value, clothing adjustment, threshold, or threshold order is invalid	`NOT VALID: review sensor readings and threshold order`
Effective WBGT reaches or exceeds the limit threshold	`CHECK: limit threshold reached`
Effective WBGT reaches or exceeds the action threshold	`CHECK: action threshold reached`
None of the preceding conditions applies	`OK`

This is the exact workbook Model_Status order. The limit warning takes precedence when both thresholds are reached.

Assumptions and limitations

Sensor readings come from a correctly set up, calibrated WBGT instrument at or near the work location.
Dry-bulb temperature is ignored in no-significant-radiant mode and required in significant-radiant mode.
All temperatures and adjustments use the selected unit consistently; the selector does not perform conversion.
No ACGIH Action Limit or TLV table, workload table, acclimatization schedule, weather dataset, or copyrighted Argonne/Liljegren estimator is embedded.
WBGT alone does not address work/rest scheduling, controls, hydration, individual susceptibility, clothing physiology, or local legal requirements.
The workbook evaluates one representative set of readings and does not calculate the 60-minute or 60-to-120-minute measurement averages described in guidance.
Comparisons use full-precision values even when displayed temperatures are rounded.

Restrictions and non-computing states

Sensor readings and thresholds must be numeric and between -100 and 250 in the selected unit. Clothing adjustment must be 0–50 temperature-difference units. The action threshold must be strictly lower than the limit threshold. Significant-radiant mode requires a valid dry-bulb value; no-radiant mode excludes it from the equation.

Errors and warnings

NOT VALID blocks interpretation of measured and effective WBGT. CHECK identifies the highest-precedence user threshold reached; it is not a declaration of regulatory noncompliance. A calculation service error is not a below-threshold result.

References

The two sensor equations, clothing adjustment, threshold margins, unit behavior, exact input guards, and status precedence were verified against the delivered workbook, its published input rules, tests, and reviewer packet. The workbook identifies these technical sources:

OSHA Technical Manual, Section III, Chapter 4 — Heat Stress — Indoor/no-solar and outdoor/direct-solar WBGT equations, effective WBGT, and measurement limitations.
NIOSH Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments — Measured WBGT definitions and equations.
OSHA Heat Hazard Recognition — On-site measurement context and clothing adjustment.

Found a problem, or have an idea?

Tell us if a result looks wrong, a label is unclear, or something is missing. We read every message.

This page is provided by LogicCommons for informational purposes only. Results are analysis outputs computed from the inputs you supply and are not engineering advice, a design, or a substitute for review by a licensed professional under the codes adopted where the work is built. Verify all inputs and results independently.

LogicCommons is in beta. If a result, label, or reference looks wrong, tell us here; we read every message.