A number of preservative manufacturers have developed carbon-based preservatives designed for above ground uses. To fulfill the requirements of Canada's Pest Management Regulatory Agency for performance data under Canadian conditions, a prototype accelerated field simulation test method had been developed and successfully tested. This report covers the design and construction of a purpose built chamber in which to conduct this test.The temperature- and humidity-controlled chamber contains metal racks, fitted with drip trays, on which samples can be placed and intermittently sprayed with deionized water to simulate rainfall. Sporing cultures of wood rotting fungi will be attached to the ceiling and outdoor air is brought in, heated and humidified, at intervals to introduce natural airspora. The chamber has been constructed to specifications.