Usually, precompliance testing is done locally, with relaxed conditions, such as in a lab on a bench. It helps identify problems that need extra attention in design. Once engineering is confident in the performance of the device, more and more rigorous testing is done, in more controlled environments (such as a screen room) to continually verify compliance. Once the device has reached the pre-production stage, where the design is finalized and the factory is building the parts, full compliance can be performed. Since most factories don't have in-house EMC testing facilities, full compliance must be performed by a certified lab and can be costly.