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How is fumigation done?

Q: What should be the concentration and quantity of formaline used for fumigation of an operation theatre by aerosol using formaline and water?

A:Formaline is a commercially available as a 40% solution of formaldehyde vapour in water. When it is heated, formaldehyde vapour is generated. Fumigation is most effective above a temperature of 20 oC and relative humidity of 65% and at temperatures below 18 oC, formaldehyde fumigation is less effective. The quantity of Formaline required is approximately 2 ml per cubic foot (0.028 m3) internal air space. There are several ways of generating formaldehyde vapour: a) a mixture of formaline and water can be heated in a thermostatically controlled heating unit like an electric frying pan (not an electric kettle as some formaline is left beneath the element) or a specifically designed vaporising unit; b) using commercially available formaldehyde generating kits; or c) mixing formaline and water with potassium permanganate crystals (This can result in a violent reaction if the correct relative concentrations of the two components are not used and is not recommended) Fumigation must be carried out only by trained personnel and decontamination efficacy must be demonstrated by placing spore strips at strategic locations around the OT and these should be later collected and incubated. Before the procedure the place must be completely sealed to prevent escape of formaldehyde vapour into other areas and this may require sealing service ducts and other holes through which fumigants may escape (including false ceiling). Following fumigation there must also be an effective means of venting or exhausting the formaldehyde that avoids the need for any person to enter the area where the formaldehyde has been released. The extract must be a total loss system with no possibility of formaldehyde going to other areas. Place the appropriate quantities of formaline and water mixture into the heater unit and when ready activate the heater and leave the room immediately. Use 100 ml formaline plus 900 ml water per 28.3 m3 (1000 ft3) of space. The door should be locked and effectively sealed around the edges with tape. After a period of not less than 12 hours (the procedure is best carried out overnight), the room must be well ventilated. Check levels of residual formaldehyde in the room with suitable air monitoring equipment (formaldameter or air sampling tubes) and one should enter only when the level of formaldehyde is below 2ppm. Formaldehyde is a scheduled chemical and has a Maximum Exposure Limit (MEL) of 2 ppm (or 2.5 mg.m-3). Concentrations encountered during fumigation are many hundreds of times higher than this so fumigation operations must be carried out only by trained personnel under strictly defined conditions. Under certain conditions formaldehyde can react with hydrochloric acid and chlorine-containing disinfectants such as hypochlorites to form bis (chlormethyl) ether, a potent lung carcinogen. Hydrochloric acid and chlorine-containing disinfectants must therefore be removed from the area before fumigation.


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