Occupational Health, Industrial Hygiene & Sports Medicine (ISO 7243)
WBGT Outdoor & Indoor Occupational Heat-Stress Formula
Calculate ISO 7243 / OSHA Wet-Bulb Globe Temperature (Outdoor Solar 0.7*Tnwb + 0.2*Tg + 0.1*Tdb vs Indoor 0.7*Tnwb + 0.3*Tg), PPE Clothing-Adjusted WBGT_eff, Radiant Globe Spread, and ACGIH Work-Rest Regime.
Protect outdoor crews and foundry workers with ISO 7243 Wet-Bulb Globe Temperature (WBGT)!
Unlike consumer weather-app "Heat Index" (measured in calm shade!), Industrial Hygienists, OSHA inspectors, military commanders, and athletics trainers prevent exertional heat stroke using ISO 7243 Wet-Bulb Globe Temperature (WBGT)—combining evaporative sweat cooling (70% weight on Natural Wet-Bulb T_nwb!), direct solar/furnace thermal radiation (150 mm matte-black Copper Globe T_g), and ambient convective air temperature (T_db)! Outdoors under direct solar load (Solar_Flag = 1), WBGT_out = 0.7 * T_nwb + 0.2 * T_g + 0.1 * T_db; indoors or at night without solar load (Solar_Flag = 0), WBGT_in = 0.7 * T_nwb + 0.3 * T_g! Adding ACGIH Clothing Adjustment Value CAV (e.g., +2.0 C for double-layer FR coveralls) yields Effective WBGT_eff compared against acclimatized work-rest screening limits!
Verify on a Construction Site Safety Audit—Natural_WetBulb T_nwb = 24.0 C (B2), Black_Globe T_g = 38.0 C (B3), Shade_DryBulb T_db = 33.0 C (B4), Direct_Solar_Load = 1 (B5), and FR_Coverall_CAV = 2.0 C (B6): Outdoor Environmental WBGT is 0.7 * 24 + 0.2 * 38 + 0.1 * 33 = 16.8 + 7.6 + 3.3 = 27.70 C (E2); PPE-Adjusted Effective WBGT_eff rises to 27.70 + 2.00 = 29.70 C (E3); Radiant Black-Globe Spread above dry air is 38.0 - 33.0 = 5.00 C (E4); and ACGIH Moderate-Work Screening Gate E5 prescribes a "50% Work / 50% Rest Cycle" (>= 28.0 C threshold)!
| ISO 7243 WBGT Metric (Tnwb=24 C, Tg=38 C, Tdb=33 C, Solar=1, CAV=+2 C) | Formula | Verified Output |
|---|---|---|
| Environmental WBGT (C) | IF(Solar=1, 0.7*Tnwb+0.2*Tg+0.1*Tdb, 0.7*Tnwb+0.3*Tg) | 27.70 C (28.20 C @ Indoor Solar=0) |
| PPE-Adjusted WBGT_eff (C) | Environmental_WBGT + Clothing_CAV | 29.70 C (27.70 C @ Breathable CAV=0) |
| Radiant Globe Spread (C) | Black_Globe_Tg - Dry_Bulb_Tdb | 5.00 C |
| ACGIH Moderate Work-Rest Gate | <28 Continuous | 28-30 50/50 | >=30 25/75 | 50% Work / 50% Rest Cycle |
ISO 7243 Outdoor / Indoor WBGT & PPE-Adjusted Screening Formula
Validate T_nwb <= T_db <= T_g + 5, Solar_Flag in {0, 1}, and Clothing_CAV in [0, 12] C!
=LET(t_wb, B2, t_gl, B3, t_db, B4, sl_f, B5, cv_c, B6, IF(OR(t_wb < -10, t_db < t_wb, t_gl < t_wb, AND(sl_f <> 0, sl_f <> 1), cv_c < 0, cv_c > 12), "Invalid WBGT Psychrometric Input", LET(wb_e, IF(sl_f = 1, 0.7 * t_wb + 0.2 * t_gl + 0.1 * t_db, 0.7 * t_wb + 0.3 * t_gl), ROUND(wb_e + cv_c, 2))))Indoor Foundry Formula (Solar = 0) & Breathable Workwear (CAV = 0 C) Checks
Switch Solar_Flag B5 to 0 (indoor radiant furnace with identical 38 C globe): Environmental WBGT E2 weights T_g at 30%, rising to 28.20 C! Or keep Solar = 1 and switch to breathable cotton shirts (CAV B6 = 0 C): WBGT_eff E3 drops to 27.70 C, clearing E5 for "Continuous Work With Hydration"!
=IF(ISTEXT(E3), E3, IF(E3 >= 30, "25% Work / 75% Rest Cycle", IF(E3 >= 28, "50% Work / 50% Rest Cycle", "Continuous Work With Hydration")))Try the example
Use the original values or change them to test your understanding.