I work in a small hospital with a bed capacity of 130 beds. Our Operating theatre needed to be fumigated and what we did was to put some +or- 0.5grams of potassium permanganate in small bowls and to it we added +or- 20mls of formaldehyde. These small bowls were placed in all the rooms. the reaction of the mixture was so instateneuos releasing a very irritating gas to the eyes the respiratory system. We sealed and closed theatre for 10 days and when we opened it for claening, that gas was still there. We had to clean it in that state because we had no choice. some nurses were put off sick because of this. How safe is this method? How do you guys do it?