WBGT rest breaks are scheduled by work intensity. Under the Standard for Work and Rest Schedules for Workers in High-Temperature Work, moderate work at a WBGT of 29.4°C requires 25% rest per hour (15 minutes), 50% at 31.1°C and 75% at 32.6°C. The thresholds for heavy work are lower, and from 25.9°C it already counts as high-temperature work.
This table is the only Taiwanese regulation that sets work and rest schedules by WBGT numbers, and many people use it to schedule rest on sites and in factories. But it was originally written for "high-temperature work" such as boiler rooms and molten metal, and outdoor work has its own rules based on heat hazard risk levels. This article explains how to read the table, how to schedule outdoor work, how to handle heat acclimatisation and hydration, and finishes with an example schedule.
WBGT Rest Break Table (Article 5, Standard for Work and Rest Schedules for Workers in High-Temperature Work)
The figures in the table are the "time-weighted average WBGT". When this value is reached, the work and rest proportion per hour is as follows:
| Work intensity | Continuous work | 75% work, 25% rest (rest 15 minutes per hour) | 50% work, 50% rest (rest 30 minutes per hour) | 25% work, 75% rest (rest 45 minutes per hour) |
|---|---|---|---|---|
| Light work | 30.6°C | 31.4°C | 32.2°C | 33.0°C |
| Moderate work | 28.0°C | 29.4°C | 31.1°C | 32.6°C |
| Heavy work | 25.9°C | 27.9°C | 30.0°C | 32.1°C |
How to read it: find the row for the work intensity, then see which column the WBGT on site falls in. For example, for moderate work with a measured WBGT of 30.2°C, which has reached 29.4°C but not 31.1°C, the schedule is 45 minutes of work and 15 minutes of rest per hour. For continuous exposure of more than one hour, the hourly average is used; for intermittent exposure, it is calculated over two hours.
How Do You Tell Light, Moderate and Heavy Work Apart?
At the same WBGT, the heavier the work, the more heat the body produces itself and the less environmental heat it can tolerate. Article 4 of the Standard classifies work as follows:
| Work intensity | Definition in the regulation | Common examples on site |
|---|---|---|
| Light work | Only arm movements to operate machinery while sitting or standing | Operating a machine panel, reading gauges, operating equipment while seated |
| Moderate work | Lifting or pushing ordinary weights while walking | Carrying building materials, pushing hand carts, walking inspections |
| Heavy work | Whole-body work such as shoveling, digging and pushing | Excavation, shoveling material, tying reinforcing bar, manual paving |
When unsure, classify it as the heavier level. Wearing non-breathable protective clothing, or a helmet and vest all day, also makes the real load heavier than the table shows.
How Do You Schedule Rest for Outdoor Work?
Article 2 of the Standard for Work and Rest Schedules for Workers in High-Temperature Work lists specified high-temperature work such as boiler rooms, metal melting and casting. For outdoor sites, roads and farm work, the regulation requires the ten heat hazard prevention measures in Article 324-6 of the Regulations on Occupational Safety and Health Facilities, which include "adjust working hours". Risk is judged by the heat hazard risk levels in the OSHA Guidelines for the Prevention of Heat Hazards in High-Temperature Work (Levels 1 to 4 by heat index).
In practice, you can schedule it like this:
- Check the heat hazard risk level before work each day: look up the heat index and level for your area on the Ministry of Labor's High-Temperature Work Protection Information Website, and plan the day's working hours. For work in direct sunshine, or in non-breathable heavy protective clothing, the guidelines require raising the level by one.
- Give heavy physical work enough rest: the OSHA guidelines state that when workers do heavy physical work, working time should be reduced and at least 20 minutes of adequate rest per hour should be given, with the measures for each level applied.
- Use on-site WBGT to catch local heat: on the same site, WBGT on a roof, steel frame or asphalt surface can be several degrees higher than in the shade (see How to Calculate WBGT for an example). Use the table above as a reference, give the hottest areas more rest, or move heavy work to the morning and evening.
- Heat hazard risk at Level 4: under Article 303-1 of the Regulations, provide shade and cooling equipment at the work area, and a rest area with a cooling effect nearby, with sufficient drinking water.
For the details of the regulations and penalties under the 2026 Occupational Safety and Health Act, see Heat Hazard Regulations and Penalties.
New Workers Need Heat Acclimatisation First
Many people who suffer heat stroke have just started a job or just returned from a long break, because their bodies have not adapted to the heat. Article 6-1 of the Standard for Work and Rest Schedules for Workers in High-Temperature Work requires employers to plan a suitable heat acclimatisation period for workers doing high-temperature work for the first time. The Ministry of Labor also reminds employers of outdoor workers to set up an acclimatisation system for new workers and increase exposure gradually.
The approach recommended by the US National Institute for Occupational Safety and Health (NIOSH) can be used directly for scheduling:
| Recipient | Day 1 | Day 2 | Day 3 | After that |
|---|---|---|---|---|
| New workers with no experience in hot environments | 20% of normal exposure time | Up to 40% | Up to 60% | Add up to 20% more each day until 100% |
| Experienced workers just returning to a hot environment | 50% | 60% | 80% | Back to 100% on day 4 |
How Should You Arrange Drinking Water?
Do not wait until you are thirsty. NIOSH recommends drinking 1 cup of water (about 240 ml) every 15 to 20 minutes when working in a hot environment, and adding electrolyte drinks if the work lasts more than 2 hours or you sweat a lot. Article 9 of the Standard for Work and Rest Schedules for Workers in High-Temperature Work also requires employers to supply sufficient drinking water and salt.
Put water near the work point, not only in the office. Arrange rest in a cool, ventilated place so that rest really cools people down.
How Is Pay Calculated for Rest Time?
Under Article 7 of the Standard for Work and Rest Schedules for Workers in High-Temperature Work, if an employer reduces working time because of this Standard, the worker's original wages must not be reduced.
A Worked Schedule: One Day for a Reinforcing Bar Crew
Suppose a reinforcing bar crew ties reinforcing bar on a sun-exposed floor slab (heavy work), and the on-site WBGT monitoring station records: 27.0°C at 8 am, 29.5°C at 10 am, 31.0°C at 12 noon, 30.4°C at 2 pm and 28.2°C at 4 pm. Compare with the heavy work row:
| Time | WBGT on site | Compared with heavy work | Schedule |
|---|---|---|---|
| Around 08:00 | 27.0°C | Reached 25.9°C, not yet 27.9°C | Can work continuously; keep drinking water as usual |
| Around 10:00 | 29.5°C | Reached 27.9°C, not yet 30.0°C | Rest 15 minutes per hour |
| Around 12:00 | 31.0°C | Reached 30.0°C, not yet 32.1°C | Rest 30 minutes per hour; move heavy work to the evening |
| Around 14:00 | 30.4°C | Reached 30.0°C, not yet 32.1°C | Rest 30 minutes per hour |
| Around 16:00 | 28.2°C | Reached 27.9°C, not yet 30.0°C | Rest 15 minutes per hour |
This only shows how to use the table, and the numbers are hypothetical. The actual schedule should also consider the day's heat hazard risk level, whether workers are acclimatised, protective equipment, and the company's own heat hazard prevention plan.
As you can see, the hard part is not looking up the table but having someone know the current temperature on site at all times. With handheld instruments, someone has to measure and record at intervals. With a fixed monitoring station, values update automatically, and when a threshold is exceeded the on-site warning light, alarm and phone notification all go off at once, so the foreman does not have to keep watching.
Make Rest Reminders Run Automatically
Heat Safety Guardian is a heat hazard alert system developed in-house by YenProtek. It calculates the WBGT heat index in real time and, when limits are exceeded, triggers on-site sound and light alarms and LINE notifications. Alert thresholds can be customised to your site, for example set to the values you use to schedule rest by work intensity. Every alarm and the environmental data at that moment are kept in the cloud, so adjusting working hours and scheduling rest is well documented. It is solar-powered with NB-IoT transmission, so even a temporary site needs no power or network cables.
To find out how many monitoring points your site needs and how to set thresholds, go to Online Quote, choose a configuration and submit, or contact us. You can also look at the Heat Safety Guardian product page first.
Frequently Asked Questions
Q1: At what WBGT should workers rest?
It depends on work intensity. Under the Standard for Work and Rest Schedules for Workers in High-Temperature Work, the thresholds for 25% rest per hour are 31.4°C for light work, 29.4°C for moderate work and 27.9°C for heavy work. For 50% rest they are 32.2°C, 31.1°C and 30.0°C. For 75% rest they are 33.0°C, 32.6°C and 32.1°C.
Q2: What temperature counts as high-temperature work?
Under Article 2 of the Standard, for specified work such as in boiler rooms, metal melting and casting, if a worker's time-weighted average WBGT over the working day reaches the value in Article 5 or higher, it counts as high-temperature work: 30.6°C for light work, 28.0°C for moderate work and 25.9°C for heavy work.
Q3: Does this table also apply to outdoor construction sites?
The table was written for the specified high-temperature work listed in Article 2 of the Standard. Outdoor work follows Article 324-6 of the Regulations on Occupational Safety and Health Facilities and the heat hazard risk levels in the OSHA guidelines. However, because the WBGT table takes work intensity into account, it is a very good reference for scheduling rest outdoors.
Q4: How long should workers rest at heat hazard Level 4?
Article 303-1 of the Regulations requires that at Level 4 and above, shade, cooling equipment, a rest area with a cooling effect and sufficient drinking water must be provided. It does not set a fixed number of minutes. For heavy physical work, the OSHA guidelines recommend at least 20 minutes of rest per hour, with the schedule adjusted by level.
Q5: Is pay deducted for rest time?
Under Article 7 of the Standard, if an employer reduces working time because of this Standard, the worker's original wages must not be reduced.
Q6: How long can a new worker work on the first day?
NIOSH recommends that new workers with no experience of hot environments have no more than 20% of the normal heat exposure on day 1, increasing by no more than 20% each day after that. Employers should increase exposure gradually following an acclimatisation schedule.
Further Reading: WBGT and Heat Hazard Series
- What Is WBGT? Wet Bulb Globe Temperature Explained (Series Overview)
- How to Calculate WBGT: Outdoor and Indoor Formulas with Examples
- What Is the Heat Index? Heat Index Chart, Levels and How It Differs from WBGT
- Heat Hazard Regulations and Penalties: What Employers Must Do Under the 2026 Occupational Safety and Health Act
- How to Apply for Heat Hazard Subsidies
- How to Choose a WBGT Meter: Handheld vs Fixed Monitoring Station
- Managing Heat Hazards on Construction Sites: Heat Stroke Prevention Checklist
References
- Ministry of Labor, Standard for Work and Rest Schedules for Workers in High-Temperature Work, Articles 2, 4, 5, 6-1, 7 and 9 (amended 1 July 2014).
- Ministry of Labor, Regulations on Occupational Safety and Health Facilities, Articles 303-1 and 324-6.
- Occupational Safety and Health Administration, Ministry of Labor, Guidelines for the Prevention of Heat Hazards in High-Temperature Work, third edition (amended 20 June 2025).
- NIOSH, Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments (2016); NIOSH recommendations on heat acclimatisation and hydration.
Article updated: 2026-11-10.
