Hi, One of my colleagues maintains that PCR must be done in three separate rooms, all with positive air pressure, and that electrophoresis of the amplicon must be done in a fourth room that has negative air pressure. This is all necessary to prevent contamination of the PCR procedures through aerosolized amplicons that might be generated through pipetting, etc. Also, he maintains that PCR done on other floors of our building can contribute to the contamination. Can you explain all of this to me??

They are correct on one level. The steps to perform PCR, must be done in separate areas with separate equipment. We and many other labs do not have the physical space to have separate rooms. We do however have separate areas, etc. The simple reason for this is that PCR generates billions of copies of the original genetic material. PCR products can indeed be aerosolized and contaminate counters, equipment, even the technician's clothes. The aerosols are not likely to contaminate other labs on other floors through the air, but likely from technicians moving between labs. We have had great success in not having contamination by being very careful in the areas where we are handling the different stages.

MH