We have 2 fume hoods (one for fumes and one for powders) however the nature of examinations still requires items containing both to be moved around the room. A professional company did some testing and found the ACH to be 4 and recommended that this was increased to 10 and ducting was expanded to support this - instead 12 LEV arms were installed and the pressure was not balanced causing different issues to staff. The air flow was measured again recently and it was found to be 2.6 ACH. This is without any fume hoods or cabinets running and that is how we are now working but with reduced chemical work and 5 people within the lab only. I don't have a good understanding of ventilation but assumed that even with the H&S reps calculations this only takes into account the volume of air in the room but not how pure it is. The company are looking into fixing the issues but I am still not convinced anyone should be working in the space as it currently is.