Rapid removal of peracetic acid fumes from isolators.

Abstract

The transfer isolator described by Trexler (1979) for protecting both personnel and animals from exposure to peracetic acid (PA) has been modified in order to reduce the time required to remove PA fumes. When a large quantity of supplies are placed in the transfer isolator, ventilation for as long as 24 h has been needed to remove all traces of PA odour from the exhaust air. Volatile peracetic and acetic acids can be converted to non-volatile salts by neutralization with an alkaline solution, such as 10% aqueous sodium carbonate. Neutralization can be carried out rapidly by spreading this alkaline solution in the same way as the acid solution. The acid odour disappears when all of the PA is neutralized; a pH indicator (p-nitrophenol) can be used to determine when the acids have been neutralized. Design of isolator The new transfer isolator (Fig. 1) has no filter since ventilation is not required to remove PA, and the 2 entry ports have been replaced by a single large entry sleeve. Gloves have been tried in various positions and seem to be situated best when placed opposite the entry sleeve; in this position the entry-port cap can be manipulated readily and supplies passed into and out of the receiving isolator. There is little need for the pump-drain of the previous model since pools of acid can be neutralized where they lie. Operation of isolator This transfer isolator is loaded with a finger atomizer containing 2% PA and the sterile neutralizer, as well as the supplies as needed. The neutralizer consists of a 10% aqueous solution of Na2C03 . IOHp (washing soda) with sufficient p-nitrophenol (1% of a saturated aqueous solution) to give a strong yellow colour, sterilized by heat or filtration. A sufficient quantity of neutralizer (twice the volume of the acid solution) should be used to react with all the acid. More than a chemical equivalent of the alkali is required to assure adequate distribution, as droplets of PA solution remain a source of fumes until neutralized. As with the earlier model, all surfaces within the isolator are wetted with the PA solution. After 20 min the neutralizing solution is placed within the atomizer and all surfaces are again wetted; care must be taken to ensure that sufficient neutralizer has been added to