At least two people, split between the two sides of the table, and it isn't a one-time credential — Ontario requires refresher training on a fixed clock.
Short answer
Where a joint health and safety committee is required, “at least two members of the committee (one representing workers and one representing persons who exercise managerial functions) must be certified.” To become certified, a person must complete both Parts 1 and 2 of the mandatory training — “Basic Certification and Workplace-Specific Hazard Training” — and refresher training is required every three years. Certification has been administered by the Chief Prevention Officer since April 1, 2012, having previously run through WSIB.
The requirement names both sides specifically — it isn't satisfied by two certified members who happen to both be on management's side, or two who are both worker representatives. On larger committees (50 or more workers, requiring at least four members under Ontario's size table), the two-certified minimum still applies as a floor, not a target; a bigger committee can certify more than two members, but the one-and-one split has to be met regardless of committee size.
Basic Certification covers the general legal and process framework common to any JHSC; Workplace-Specific Hazard Training is the second, separate component covering the actual hazards of that particular workplace. Completing only Basic Certification doesn't make someone a certified member under the Act — both parts are required, and the same two-part structure explains why certification earned at one workplace doesn't automatically transfer its workplace-specific half to a different site, the same portability gap covered in whether every worker needs site orientation.
Certification isn't permanent — refresher training is required every three years, and a committee that lets its only certified members lapse no longer meets the statutory minimum even if it technically still has “two certified people” on paper from years earlier. Building the three-year renewal into a recurring calendar item is the practical fix; discovering the lapse when a work refusal happens and a certified member needs to be part of the investigation is the expensive way to find out.
The certified-member training structure described here is Ontario's. Even the underlying committee threshold isn't uniform across the country — Saskatchewan requires a JHSC once a workplace reaches just 10 workers, against the 20-worker line used by Ontario, BC, Alberta and most other jurisdictions, which is the kind of variation that makes it worth confirming your own province's certification regime rather than assuming Ontario's applies. See joint health and safety committee and JHSC minutes and follow-through for how the certified members' role continues once the committee is actually meeting.
A 30-minute call is enough to tell you whether your JHSC's certification status would survive a Ministry inspection today.
