Effective cleanroom disinfection

A significant amount of time and money is spent on testing and validating the microbial activity of cleanroom disinfectants.

However, the effectiveness of the disinfectant in laboratory tests is not the end of the validation process. The way in which the disinfectant is used can have a significant impact on the overall effectiveness of the product and subsequent environmental results obtained. The choice of presentation for different cleanroom areas includes: • ready-to-use disinfectant in trigger sprays, aerosols or 5-litre containers; • impregnated wipes of various sizes in pouches, sachets or tubs; • concentrates, powder or tablets to make up into a solution in a bucket; • unit dose concentrates that reduce the risk of dilution error; • fogging or gassing with a suitable agent Trigger sprays offer a convenient and economical solution. They have significant advantages, which include an adjustable nozzle so liquid can be dispensed as a jet or a spray, enabling thorough wetting of the surface and ensuring that disinfection procedures are effective; they are environmentally friendly as they contain no propellants that require special disposal procedures; all of the liquid can be dispensed from a trigger spray, so there is no wastage, making them a cost effective solution compared with an aerosol.

Validated design But there is a potential drawback with some trigger sprays, as contaminated air can be drawn back into the bottle, compromising the sterility of the liquid. Validation work in the licensed pharmacy unit of the Queen Elizabeth Hospital in Birmingham, UK, identified that a trigger spray alcohol had been contaminated with fungal spores only eight hours after opening.¹ Trigger spray systems are available that resolve this problem, providing a system with the benefits of a trigger spray while guaranteeing the integrity of the contents. The new validated² design operates as a closed system, preventing air being drawn back into the bottle and so eliminating the possibility of contamination of the liquid. The liquid is held inside a medical grade bag – the function of the bottle is simply to enclose and protect the bag in use. All points of entry into the bag, including the dip-tube, are completely sealed, thereby creating a closed system. In these critical zones (Grade A or B) the disinfectant must be sterile³ and its application carefully controlled, because residues and particulates must be kept to a minimum. Low particulate impregnated wipes offer an ideal solution in these situations. The impregnate (alcohol, biocide or neutral detergent for pre-cleaning) is applied evenly and precisely where required – unlike sprays that can pool in difficult-to-reach areas, leaving residues or damaging equipment. Impregnated wipes are available in individual sachets, resealable pouches or tubs. It is important to ensure that the grade of wipe is sufficient for a critical area and that the wipes can be easily removed from the packaging while wearing gloves without creating particulates. Specific unit dose concentrates are an ideal means of handling disinfectants used in large quantities, for instance on walls and floors. They not only ensure the sterility of the concentrate but minimise direct handling prior to use, reducing the risk of dilution errors and spillages. To avoid recontamination of cleaned and disinfected surfaces, it is preferable that the cleaning solution is isolated from soiled solutions. This objective is difficult to achieve using a single bucket system (Figure 1), because the dirty mop head must be returned to the bucket containing the disinfectant solution in order to apply more solution to the surface. This process inevitably contaminates the original disinfectant solution.

Environmental results Contamination can be reduced using a triple bucket system that ensures soiled disinfectant has been rinsed from the mop before it is inserted into the disinfectant solution again. Bucket 1 contains the disinfectant solution, bucket 2 contains water of suitable grade and bucket 3 is empty and ready for waste. The simple application protocol is shown below in table 1. Work carried out by Dr Smith of Aston University has proven that the use of a multiple bucket cleaning system can have a significant effect on the environmental results. The full case study was printed in EJHP in January 2005.⁴ He concluded from work carried out over three months, in three different grades of room (using a single bucket system, a triple bucket system with standard hospital disinfectant and a triple bucket with sterile specialist cleanroom disinfectants), that the use of a triple bucket system and specialist cleanroom disinfectants significantly improved the environmental results, compared with traditional cleaning methods in a non sterile room and an isolator room. The results in the sterile preparation room remained within the appropriate standards. As part of the study, Dr Smith measured the bioburden of the disinfectant solution before and after use for a single bucket system in three different grades of room. The bioburdens were tested using a pharmacopœial method for Total Viable Counts. The results are for 10ml of solution. They showed that the average number of CFUs for used disinfectant in a single bucket system were 158, 326 and 0.4 for the three different grades of room. The bucket system showed no contamination of the disinfectant solution after use in any of the rooms. Dr Smith's research also showed a significant improvement in the initial bioburden of the disinfectant solution by switching to reverse osmosis water for the dilution instead of mains potable water. The correct grade of water for the room being cleaned or disinfected should always be used – in a Grade B room the water used for dilution should also be sterile. Various designs of multiple bucket system are available and consideration needs to be given to the size of the cleanroom and the storage of the bucket system. Some systems are specifically designed for smaller units and will fit under a bench.

Easy efficiency The system chosen must be suitable for autoclaving so that it does not introduce contaminants into the cleanroom each time it enters. A flat mop head is easy and efficient to use on walls, floors and ceilings. The mopheads should be single use and sterile for use in Grade A and B areas. The correct grade of mop should be used for the grade of room: 100% polyester, polyester/cellulose blends and PU sponge are all used to make cleanroom mopheads. The mop frame should also be autoclavable and lightweight, especially if ceilings are very high. A universal joint allows the mop head to be tilted to mop behind equipment. As always, mopping should be carried out to a validated procedure by trained operators. To keep the mop as clean as possible during cleaning, work from the dirtiest area to the cleanest. Therefore clean ceilings and walls before floors, wipe ceilings and walls starting at the filters and floors at the furthest point from the door. Mopping should be carried out in overlapping parallel lines, ensuring that no surface remains unwiped.

Avoid contamination Finally, an alternative method of applying disinfectant to large areas is with an impregnated mop wipe. These can save additional time by eliminating the need to mix concentrate into a solution or use a bucket system and they remove the risk of dilution error. They also eliminate the need to source water of suitable quality for dilution, a major inconvenience which has the potential of contamination if the water source is outside the cleanroom area. The use of an impregnated mop wipe system also ensures the risk of the cleaning fluid becoming contaminated is avoided. Disposal is simplified as there is no need to dispose of unused disinfectant in the drainage system. So as can be seen, a cleanroom may need several different application methods for a disinfectant to ensure the most efficient and effective procedure. Each application method should be validated and carried out by trained operators to a standard procedure.