Annex 3 of NR15 – Tolerance Limits for Heat Exposure

(SEPRT Ordinance No. 1359, December 9, 2019)

Summary:

1. Objectives
2. Characterization of Unhealthy Activity or Operation
3. Technical Report for Characterization of Occupational Heat Exposure

1. Objectives

1.1 The objective of this Annex is to establish criteria to characterize unhealthy activities or operations resulting from occupational heat exposure in enclosed environments or environments with an artificial heat source.

1.1.1 This Annex does not apply to occupational activities performed in open environments without an artificial heat source.

2. Characterization of Unhealthy Activity or Operation

2.1 The quantitative evaluation of heat must be carried out based on the methodology and procedures described in the Occupational Hygiene Standard NHO 06 (2nd edition – 2017) by FUNDACENTRO, considering the following aspects:

a) Determination of thermal overload through the IBUTG index – Wet Bulb Globe Thermometer Index;

b) Measurement equipment and methods of assembly, positioning, and procedures for their use in the evaluated locations;

c) Procedures regarding the conduct of the evaluator; and

d) Measurements and calculations.

2.2 The metabolic rate must be estimated based on the comparison of the activity performed by the worker with the options presented in Table 2 of this Annex.

2.2.1 If a specific activity is not presented in Table 2 of this Annex, the metabolic rate value should be obtained by association with a similar activity in the mentioned Table.

2.3 Activities or operations performed in enclosed environments or environments with an artificial heat source are characterized as unhealthy whenever the measured average IBUTG exceeds the occupational exposure limits established based on the Wet Bulb Globe Thermometer Index presented in Table 1 and determined from the metabolic rate of activities presented in Table 2 of this Annex.

2.4 The average Wet Bulb Globe Thermometer Index and the average Metabolic Rate to be considered in the heat exposure evaluation must be those obtained over a continuous period of 60 minutes, resulting in the most critical exposure condition.

2.4.1 The quantitative evaluation must be representative of the exposure, disregarding occasional or non-routine exposure situations in which workers are not exposed daily.

2.5 The occupational heat exposure limits are presented in Table 1 of this Annex for different average metabolic rate values.

2.6 Situations of occupational heat exposure characterized as unhealthy will be classified as of medium degree.

3. Technical Report for Characterization of Occupational Heat Exposure

3.1 The characterization of occupational heat exposure must be documented in a technical report that includes at least the following items:

a) Introduction, objectives of the work, and justification;

b) Risk assessment, as described in item 3.2 of Annex III of NR-09; (amended by MTP Ordinance No. 426, October 7, 2021)

c) Description of the methodology and evaluation criteria, including locations, dates, and times of measurements;

d) Specification and identification of the measurement devices used and their respective calibration certificates according to NHO 06 by Fundacentro, when using the IBUTG meter;

e) Evaluation of the results;

f) Description and evaluation of control measures already adopted, if any; and

g) Conclusion indicating whether or not the situation is characterized as unhealthy.

Table 1 – Occupational Heat Exposure Limits

Metabolic Rate (W)	IBUTG Limit (°C)
100	33.7
102	33.6
104	33.5
106	33.4
108	33.3
110	33.2
112	33.1
115	33.0
117	32.9
119	32.8
122	32.7
124	32.6
127	32.5
129	32.4
132	32.3
135	32.2
137	32.1
140	32.0
143	31.9
146	31.8
149	31.7
152	31.6
155	31.5
158	31.4
161	31.3
165	31.2
168	31.1
171	31.0
175	30.9
178	30.8
182	30.7
186	30.6
189	30.5
193	30.4
197	30.3
201	30.2
205	30.1
209	30.0
214	29.9
218	29.8
222	29.7
227	29.6
231	29.5
236	29.4
241	29.3
246	29.2
251	29.1
256	29.0
261	28.9
266	28.8
272	28.7
277	28.6
283	28.5
289	28.4
294	28.3
300	28.2
306	28.1
313	28.0
319	27.9
325	27.8
332	27.7
339	27.6
346	27.5
353	27.4
360	27.3
367	27.2
374	27.1
382	27.0
390	26.9
398	26.8
406	26.7
414	26.6
422	26.5
431	26.4
440	26.3
448	26.2
458	26.1
467	26.0
476	25.9
486	25.8
496	25.7
506	25.6
516	25.5
526	25.4
537	25.3
548	25.2
559	25.1
570	25.0
582	24.9
594	24.8
606	24.7

Table 2 – Metabolic Rate by Activity Type

Activity Type	Metabolic Rate (W)
Sitting
At rest	100
Light work with hands	126
Moderate work with hands	153
Heavy work with hands	171
Light work with one arm	162
Moderate work with one arm	198
Heavy work with one arm	234
Light work with two arms	216
Moderate work with two arms	252
Heavy work with two arms	288
Light work with arms and legs	324
Moderate work with arms and legs	441
Heavy work with arms and legs	603
Standing, crouched, or kneeling
At rest	126
Light work with hands	153
Moderate work with hands	180
Heavy work with hands	198
Light work with one arm	189
Moderate work with one arm	225
Heavy work with one arm	261
Light work with two arms	243
Moderate work with two arms	279
Heavy work with two arms	315
Light work with body	351
Moderate work with body	468
Heavy work with body	630
Standing, moving
Walking on a flat surface
1. Without load
2 km/h	198
3 km/h	252
4 km/h	297
5 km/h	360
2. With load
10 kg, 4 km/h	333
30 kg, 4 km/h	450
Running on a flat surface
9 km/h	787
12 km/h	873
15 km/h	990
Climbing ramp
1. Without load
with 5° incline, 4 km/h	324
with 15° incline, 3 km/h	378
with 25° incline, 3 km/h	540
2. With 20 kg load
with 15° incline, 4 km/h	486
with 25° incline, 4 km/h	738
Descending ramp (5 km/h) without load
with 5° incline	243
with 15° incline	252
with 25° incline	324
Climbing stairs (80 steps per minute – step height 0.17 m)
2. Without load	522
With 20 kg load	648
Descending stairs (80 steps per minute – step height 0.17 m)
Without load	279
With 20 kg load	400
Moderate work with arms (e.g., sweeping, warehouse work)	320
Moderate work of lifting or pushing	349
Work pushing wheelbarrows on flat surface, with load	391
Work carrying weights or with vigorous arm movements (e.g., work with a scythe)	495
Heavy work of lifting, pushing, or dragging weights (e.g., shoveling, trenching)	524