VANCOUVER - Concerns about marijuana smoke seeping in to the ventilation system and misuse of city property have prompted the closure of the Vancouver Aquatic Centre on April 20 while an annual pot protest is held nearby.

Vancouver Park Board Chairwoman Sarah Kirby-Yung says the facility at Sunset Beach will be closed Wednesday, while thousands of pot smoking protesters are expected to pack the beach for the 4-20 Smoke Out celebration of cannabis culture.

Kirby-Yung says large intake fans at the Aquatic Centre control humidity and can't safely be turned off, creating the possibility that smoke from the marijuana protest will be drawn into the building.

Vancouver police estimated that last year's crowd reached 15,000, and Kirby-Yung says there is a concern some at this protest could use the centre inappropriately.

The annual 4-20 protest has been growing in Vancouver since 1995 when about 200 people attended a rally in Victory Square on the city's Downtown Eastside.

The event has been held at the art gallery in downtown Vancouver for several years, but construction at that site prompted organizers to make the unauthorized move to Sunset Beach for this year.