The smoke testing can and should be carried out by a trained employee of the LARC doing the work. We would at least have two persons carrying out this test with our supervisor acting as the witness. For good measure it can be be witnessed by a independent person appointed by the Client (e.g. analyst). The witnessing of the smoke test is not part of the 4-stage clearance process, so it is not a prerequsite that it is witnessed independently just good practice, that's all. There is no mention of witnessing in Asbestos: The licensed contractors' guide, Chapter 6, para 50 to 52 (HSG247) but as I said it is good practice to have this witnessed.