PHS App

Predicted Heat Strain App assesses heat stress at work using the Predicted Heat Strain (PHS) model of ISO 7933:2023, the international standard for the analytical evaluation of heat stress.

Describe the worker, the climate, the activity and the clothing, and the app calculates:
• the maximum allowable exposure time, and whether it is limited by body core temperature or by water loss
• rectal temperature and cumulative water loss, minute by minute
• the predicted sweat rate

FEATURES
• Several work phases in sequence (for example work, rest, work). Body temperature and water loss carry over from one phase to the next.
• Enter your own values, or choose from typical activities and clothing ensembles
• Radiant heat as globe temperature or mean radiant temperature; humidity as relative humidity or vapour pressure
• Metabolic rate in W or W/m², with the conversion shown
• Options for acclimatised workers and for workers who can drink freely
• Inputs are checked against the model's validated ranges, with clear warnings
• Charts of rectal temperature and water loss, with limit lines, phase bands and your own notes
• A formatted report you can print or save as a PDF
• Scenarios are saved as .ete2 files that you can keep, share and reopen; older .ete files can be imported
• Includes the five worked examples of ISO 7933 Annex F
• Works offline. Your scenarios stay on your device.

WHO IT IS FOR
Occupational hygienists, health and safety professionals, engineers and students assessing hot working conditions such as foundries, mines, kitchens, laundries and outdoor work in summer.

IMPORTANT
Results are predictions from the ISO 7933 model for a standard worker. They support, but do not replace, professional judgement, and physiological monitoring where the standard calls for it. This app is not a medical device.

Developed by Vinod Gopaldasani.