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Ontario OHCOW Humidex Heat Response Plan — Heat Stress Work/Rest Limits

Ontario OHCOW Humidex-Based Heat Response Plan for indoor workers. Uses Canadian Humidex (air temperature + humidity-derived discomfort index) with PPE and acclimatization adjustments to assign tiered work/rest schedules. Widely used in Ontario workplaces as a practical alternative to WBGT for indoor environments.

Open Ontario OHCOW Humidex Heat Response Plan in the interactive Guidance Wiki →

Authority

Occupational Health Clinics for Ontario Workers (OHCOW)

Jurisdiction

Ontario Canada

Legal status

Guidance

Rule type

Schedule Engine

Standard ID

HGC-067

Governing formula

No standalone formula is published for this standard; see programmable logic and parameters below.

Work/rest limits

Light work

Air temp (°C)	30% RH	40% RH	50% RH	60% RH	70% RH	80% RH	90% RH	100% RH
24	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr
26	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr
28	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr
30	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work
32	45 / 15 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work
34	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
36	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
38	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
40	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work

Moderate work

Air temp (°C)	30% RH	40% RH	50% RH	60% RH	70% RH	80% RH	90% RH	100% RH
24	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr
26	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr
28	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr
30	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work
32	45 / 15 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work
34	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
36	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
38	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
40	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work

Heavy work

Air temp (°C)	30% RH	40% RH	50% RH	60% RH	70% RH	80% RH	90% RH	100% RH
24	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr
26	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr
28	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr
30	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work
32	45 / 15 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work
34	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
36	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
38	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
40	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work

Very heavy work

Air temp (°C)	30% RH	40% RH	50% RH	60% RH	70% RH	80% RH	90% RH	100% RH
24	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr
26	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr
28	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr
30	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	60 / 0 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work
32	45 / 15 min work/rest per hr	30 / 30 min work/rest per hr	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work
34	15 / 45 min work/rest per hr	15 / 45 min work/rest per hr	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
36	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
38	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work
40	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work	Stop work

Inputs

Required inputs: airTempC, relativeHumidity, workload

Optional inputs: ppe, acclimatization

Sources

• 🇨🇦 Ontario OHCOW Humidex-Based Heat Response Plan for Indoor Workers — Occupational Health Clinics for Ontario Workers (OHCOW) (guidance)

Related standards

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• ACGIH TLV / Action Limit
• TB MED 507 Heat Categories
• NIOSH 2016-106 Table 6-2
• AAFA Guide to Protecting Workers from Heat Stress 2026
• India WBGT Work/Rest Bands (source needs verification)
• Vietnam QCVN 26:2016/BYT
• Hong Kong Labour Department
• Brunei SHENA Heat Stress Guidance
• Malaysia DOSH Heat Stress Guidelines 2016
• El Salvador Decreto No. 89 (TGBH)
• Taiwan High-Temperature Work/Rest Standard
• and 18 more with the same rule type