The OS — formally the Gledhill-Shaw Occupational Skills Assessment, also called the Gledhill-Shaw OS Firefighter Test — is a firefighter selection assessment provided by Gledhill/Shaw Enterprise Ltd. Each department that uses it runs it itself, and FireStart couldn't find one that names it in a current posting.
The OS is a single written assessment with a time limit of 2 hours 15 minutes. Some older prep material describes a longer, multi-part format — that is out of date. The question count and section-by-section breakdown are not consistently published, so treat any exact numbers you see elsewhere with caution.
The OS is administered directly by the hiring fire department — there is no centralized testing body like OFAI or FireOntario. Each department sets its own passing standard, so check the recruitment package for your competition.
Note: Gledhill/Shaw Enterprise Ltd. does not maintain a public website. All information about the OS test comes from the fire departments that use it. This makes preparation resources scarce — which is exactly why thorough preparation matters.