As of January 1, 2026, construction sites in Ontario with 20 or more workers and projects lasting longer than three months are legally required to have Automated External Defibrillators (AEDs) on site. The key elements are that the project has 20 or more workers and is expected to last at least three months. Short-term projects under three months are exempt, but having an AED is still recommended as a best practice. WSIB does have a rebate program available.