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WBGT and heat exposure limit (Brazilian NR-15)

Assesses activity heat stress with WBGT (IBUTG) and compares it with occupational exposure limits (unhealthy working conditions) and regulatory action levels.

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Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.

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Method · Limits of application

NR-15 Annex 3 Ordinance 1359/2019 and NR-9 Annex III: WBGT without/with sun; clothing adjustment; metabolic-rate table

The NR-15 Annex 3 unhealthy-work limit concerns enclosed environments or those with an artificial heat source; the annex excludes outdoor work without an artificial source. Assessment requires NHO 06 procedures and representative averages of the 60 consecutive minutes of most critical exposure. The calculation alone does not establish an unhealthy-work condition without the assessment and report required by the standard. NR-9 preventive requirements have their own scope and must not be confused with this exclusion.

Required fields: 0/7 completed

Complete all required fields. Optional fields are marked.

Activity location required

Is there direct solar exposure at the measurement point? required

Natural wet-bulb temperature (tbn) required°C · range 0–45

Globe temperature (tg) required°C · range 0–90

Dry-bulb temperature (tbs), only with solar exposure (optional)°C · range 0–60

Mean metabolic rate of the activity (Table 2 of Brazilian NR-15) requiredW · range 100–606

Clothing required

Hooded clothing (+1 °C) required

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Conditions of use

Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.

Documented parameters

Activity location
Is there direct solar exposure at the measurement point?
Natural wet-bulb temperature (tbn) · °C
Globe temperature (tg) · °C
Dry-bulb temperature (tbs), only with solar exposure · °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15) · W
Clothing
Hooded clothing (+1 °C)

6/6 reference cases checked. Numerical tests are not clinical validation.

Sources and documentation

Documented formula

Transcribed from the source or a recorded revision; this is not a clinical recommendation.

Without solar load: IBUTG = 0.7 tbn + 0.3 tg. With solar load: IBUTG = 0.7 tbn + 0.1 tbs + 0.2 tg (Fundacentro NHO 06).

Add clothing adjustment (Table 4, Annex 3, NR-9; hood +1 °C). Compare with maximum IBUTG in Table 1, Annex 3, NR-15 (exposure limit) and Table 1, Annex 3, NR-9 (action level), using the highest tabulated metabolic-rate row not exceeding the entered rate.

References

Identifier: ibutg

Original clinical content: Brazilian Portuguese.

Method version

NR-15 Annex 3 Ordinance 1359/2019 and NR-9 Annex III: WBGT without/with sun; clothing adjustment; metabolic-rate table

ibutg@native-2026-10-03+f224aedece8f

Brasil. Ministério do Trabalho e Emprego. Norma Regulamentadora nº 15 (NR-15): Atividades e Operações Insalubres, com o Anexo 3 alterado pela Portaria SEPRT nº 1.359/2019.

The bibliographic edition identifies the source. By itself, it proves neither full conformity of the formula nor clinical approval.

Synthetic cases checked (6)

Synthetic cases for checking the implementation, with no patient data.

Case 1

reference-001

Inputs

Activity location: Indoor environment or artificial heat source
Is there direct solar exposure at the measurement point?: No
Natural wet-bulb temperature (tbn): 25 °C
Globe temperature (tg): 40 °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15): 300 W
Clothing: Uniform (trousers and long-sleeved shirt) or fabric coveralls: +0
Hooded clothing (+1 °C): No

{
  "amb": "fechado",
  "solar": "0",
  "tbn": 25,
  "tg": 40,
  "m": 300,
  "roupa": "0",
  "capuz": false
}

Expected result

{
  "ibutg": 29.5,
  "lim": 28.2,
  "acao": 25
}

Actual result

{
  "ibutg": 29.5,
  "base": 29.5,
  "lim": 28.2,
  "acao": 25
}

Case 2

reference-002

Inputs

Activity location: Indoor environment or artificial heat source
Is there direct solar exposure at the measurement point?: No
Natural wet-bulb temperature (tbn): 22 °C
Globe temperature (tg): 30 °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15): 200 W
Clothing: Uniform (trousers and long-sleeved shirt) or fabric coveralls: +0
Hooded clothing (+1 °C): No

{
  "amb": "fechado",
  "solar": "0",
  "tbn": 22,
  "tg": 30,
  "m": 200,
  "roupa": "0",
  "capuz": false
}

Expected result

{
  "ibutg": 24.4,
  "lim": 30.3,
  "acao": 27.5
}

Actual result

{
  "ibutg": 24.4,
  "base": 24.4,
  "lim": 30.3,
  "acao": 27.5
}

Case 3

reference-003

Inputs

Activity location: Indoor environment or artificial heat source
Is there direct solar exposure at the measurement point?: No
Natural wet-bulb temperature (tbn): 25 °C
Globe temperature (tg): 32 °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15): 250 W
Clothing: Uniform (trousers and long-sleeved shirt) or fabric coveralls: +0
Hooded clothing (+1 °C): No

{
  "amb": "fechado",
  "solar": "0",
  "tbn": 25,
  "tg": 32,
  "m": 250,
  "roupa": "0",
  "capuz": false
}

Expected result

{
  "ibutg": 27.1,
  "lim": 29.2,
  "acao": 26.1
}

Actual result

{
  "ibutg": 27.1,
  "base": 27.1,
  "lim": 29.2,
  "acao": 26.1
}

Case 4

reference-004

Inputs

Activity location: Outdoors, without an artificial heat source
Is there direct solar exposure at the measurement point?: Yes
Natural wet-bulb temperature (tbn): 25 °C
Dry-bulb temperature (tbs), only with solar exposure: 32 °C
Globe temperature (tg): 45 °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15): 360 W
Clothing: Uniform (trousers and long-sleeved shirt) or fabric coveralls: +0
Hooded clothing (+1 °C): No

{
  "amb": "aberto",
  "solar": "1",
  "tbn": 25,
  "tbs": 32,
  "tg": 45,
  "m": 360,
  "roupa": "0",
  "capuz": false
}

Expected result

{
  "ibutg": 29.7,
  "lim": 27.3
}

Actual result

{
  "ibutg": 29.7,
  "base": 29.7,
  "lim": 27.3,
  "acao": 23.9
}

Case 5

reference-005

Inputs

Activity location: Indoor environment or artificial heat source
Is there direct solar exposure at the measurement point?: No
Natural wet-bulb temperature (tbn): 22 °C
Globe temperature (tg): 30 °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15): 200 W
Clothing: Vapor-barrier coveralls: +10 °C
Hooded clothing (+1 °C): No

{
  "amb": "fechado",
  "solar": "0",
  "tbn": 22,
  "tg": 30,
  "m": 200,
  "roupa": "10",
  "capuz": false
}

Expected result

{
  "ibutg": 34.4,
  "base": 24.4
}

Actual result

{
  "ibutg": 34.4,
  "base": 24.4,
  "lim": 30.3,
  "acao": 27.5
}

Case 6

reference-006

Inputs

Activity location: Outdoors, without an artificial heat source
Is there direct solar exposure at the measurement point?: Yes
Natural wet-bulb temperature (tbn): 25 °C
Globe temperature (tg): 45 °C
Mean metabolic rate of the activity (Table 2 of Brazilian NR-15): 300 W
Clothing: Uniform (trousers and long-sleeved shirt) or fabric coveralls: +0
Hooded clothing (+1 °C): No

{
  "amb": "aberto",
  "solar": "1",
  "tbn": 25,
  "tg": 45,
  "m": 300,
  "roupa": "0",
  "capuz": false
}

Expected result

{
  "error": true
}

Code and reproducibility

This tool’s code on GitHub

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Sources, version and reproduction instructions

The code tests are technical checks. Clinical approval and professional translation review are recorded separately.

Relationship with cancer research

General context — relationship to be defined

A resource for general clinical contexts. This edition does not assign a specific oncological relationship; selecting it for a study requires a justified question, population and purpose.