The OSSA concept was first developed in 1994/95 as a result of the implementation of the Workplace Health & Safety Agency's Core Certification Program. Though the Certification Program proved successful in other economic sectors, it was found that it did not represent the needs of Ontario's small business community and service sector employers.
Through the creation of a more suitable certification program for the service sector industry, it became obvious that the service sector's unique Health & Safety needs were not being adequately addressed by the existing Health & Safety system in Ontario.
Service sector members typically cope with high employee turnover, large part-time staff, regular patterns of seasonal employment, and different hazards then are faced in an industrial or manufacturing environment. The service sector required an affordable, flexible approach to Health & Safety that could accommodate the ongoing demand to train new staff and focused on the Health & Safety concerns of services sector employers.
In response to these concerns, and to ensure that the financial contribution made by service sector employers be directed to relevant, sector-specific programs and services, the Ontario Service Alliance (now OSSA) and the Industrial Accident Prevention Association developed a new Basic Health & Safety Training Program. It was at this time that OSSA began to receive funding to establish the first Health & Safety organization completely dedicated to service industry professionals in Ontario.
With more than 81,000 member firms across 5 service sub-sectors, the OSSA delivers customized Health & Safety support, consultation and resources to a service industry that employs over 70% of the people who live in Ontario.

The Ontario Service Safety Alliance (OSSA) was officially incorporated and received formal designation as a safe workplace association in 1997.
That contractors you hire should provide you with a "WSIB Clearance Certificate" showing that their firm is registered with the Workplace Safety & Insurance Board, and their workers are covered under worker's compensation.