WorkSafeBC clearance is the important one
A clearance letter confirms a contractor is registered and in good standing with WorkSafeBC. If an uninsured worker is injured on your property, you as the person who engaged them can be assessed for the premiums that should have been paid, and in some circumstances for more than that. The letter is free, instant, and verifiable directly through WorkSafeBC using the contractor business number, so there is no reason to accept a verbal assurance.
Liability insurance and what it is for
Commercial general liability covers damage caused during the work: overspray onto a vehicle, a grinder cord through a wall, a flooded basement from a hose left running. Ask for the certificate rather than the promise, check the coverage limit and check the expiry date. On a commercial project the building owner or property manager will usually specify a minimum limit and want to be named, which is a normal request and one a real contractor handles routinely.
Registration and where the business lives
A registered BC business number, a real address, and a phone number that is answered. None of these guarantee quality, and their absence is informative. Concrete coating attracts out-of-town crews who work a region for a season and disappear, which matters a great deal when a warranty question comes up in year three. Ask how long they have worked in this valley and who did their last five jobs locally.
The dust question specifically
Concrete grinding without extraction produces respirable crystalline silica, which is a regulated occupational hazard in BC with real exposure control requirements. A crew grinding indoors without HEPA extraction is both leaving your building full of dust and working outside the regulations. It is a reasonable thing to ask about, and the answer tells you a great deal about how the rest of the job will be run.
Want this answered for your slab?
Free site visit with a moisture reading, then a written fixed price. Across the BC Interior.