Cleaning and hygiene have always been imperative to prevent the potential survival and spread of microorganisms. In many cleanrooms and sterile environments, whole room disinfection has been the best process to achieve this, since it enables difficult to reach places to be thoroughly disinfected. There are a range of techniques available to achieve this, from ultraviolet light to ionisation, but one of the most popular is chemical misting. Technically speaking, a decontamination system that distributes a biocide via an automated spray, mist, fog, vapour, or other technique, is considered an 'airborne automated disinfection system'.
The most common active active is hydrogen peroxide
Fogging machines are not a new decontamination method – after all, they are often used by pharmaceutical cleanroom equipment manufacturers for environmental disinfection of hard-to-reach areas, such as pipework. Despite this, their use has become much more popular during the pandemic across other industries too.
Used to disinfect, sanitise, or restrict the growth of mould, bacteria, and viruses, the fogging machines can sanitise large internal spaces, common touch surfaces and tricky areas effectively. It makes this method of disinfection particularly suited to environments that need to be kept sterile or where infection can easily and quickly spread too, such as hospitals, veterinary clinics, schools, public transport, and other public facilities.
In addition to whole rooms, automated airborne disinfection is a measure required for small enclosures, such as for biosafety cabinets and hatcheries.
How it works
A chemical disinfectant, the most common active being hydrogen peroxide, is loaded into a fogging unit to produce and disperse an aerosol around the room or into a small enclosure, to reduce the numbers of microorganisms on surfaces and areas that are difficult to access. The equipment immerses the atmosphere with the disinfectant mist and is then allowed a pre-determined period of time to settle out of the air and onto the surfaces.
All airborne automated disinfection systems must be tested, in combination with their active biocidal products (for example, hydrogen peroxide) to confirm their efficacy. Prior to October 2020, regulators required efficacy data produced using the French standard NFT 72-281, a challenging test against a wide range of microbiological organisms (such as bacteria, viruses, fungi, yeasts, spores, mycobacteria, and bacteriophage) with soiling conditions relevant to the claimed use scenario.
Automated airborne disinfection is required for small enclosures such as biosafety cabinets
However, this has recently been superseded by a new European standard: BS EN 17272:2020 Chemical Disinfectants and Antiseptics – Methods of airborne room disinfection by automated process – Determination of bactericidal, mycobactericidal, sporicidal, fungicidal, yeasticidal, virucidal and phagocidal activities. According to this, manufacturers must have their systems tested to ensure compliance, or have their solutions booked in to be tested. It is important to note that the product-device combination cannot be separated for the testing by this standard.
What the EN 17272 test involves
The EN 17272 standard is designed to determine activity of processes used in the medical, veterinary, food, industrial, domestic, and institutional areas, using automated processes for distributing chemicals by air diffusion with no operator manually applying the disinfectant. This includes the disinfection of nonporous surfaces but not that of the air.
The objective of the described processes is to disinfect the surfaces of the overall area including the external surfaces of the equipment contained in such rooms, and prove efficacy against vegetative bacteria, mycobacteria, bacterial spores, yeasts, fungal spores, viruses, and bacteriophages.
Whereas the previous standard, NFT 72-281, solely focused on evaluating biocidal activity of air surface disinfection processes, the EN 17272 test method consists of two parts, testing both effectiveness and distribution. The efficacy part of the test ensures that the minimum microorganism reduction requirements are met for each claimed activity and for the targeted application area, whilst the distribution test is designed to evaluate the distribution efficiency process throughout the test enclosure or room.
The EN 17272 test method tests both effectiveness and distribution
For the efficacy test, each of the biocidal activities can be tested individually, but to comply with EN 17272, it must show at least bactericidal and yeasticidal activity.
The method involves placing a small number of test organisms or virus on stainless steel discs and placing them around the room, according to defined standards. The device is then left to run for its cycle. At the end of the test, the number of organisms or virus surviving on the discs is counted. This test data can then be used to report the specific disinfectant activity of the automated airborne disinfection system.
To consider the bactericidal product, a log reduction of not less than five in the number of viable cells must be demonstrated. For fungicidal, yeasticidal, virucidal, phagocidal, tuberculocidal and mycobactericidal activities, a reduction of at least four logarithms in the number of viable organisms must be shown. For efficacy against spores, a logarithmic reduction of at least four must be demonstrated in the medical area.
The distribution test must always be carried out under the same conditions as the efficacy test and is always carried out with Staphylococcus aureus, regardless of the activity to be declared. For this, eight supports are distributed in the test chamber in certain positions and orientations. To pass the test, a reduction of at least five logarithms must be demonstrated on all supports.
Challenges ahead
The introduction of this new standard means that all airborne automated disinfection systems must now meet the new requirement. However, this is not proving easy for UK-based manufacturers to action due to a lack of commercial testing firms on home ground. In normal times, companies would send their systems to one of the many labs in mainland Europe to secure validation. Unfortunately, a combination of challenges caused by Brexit and coronavirus has meant that this route is not a quick or straightforward process.
However, independent microbiological testing house, MSL Solution Providers, has recently added the EN 17272 standard to its roster of services and can test automated airborne systems in its brand new purpose-built lab. This building has been specially commissioned for this process and is equipped for both whole rooms and small enclosure testing.
Efficacy testing is a crucial part of achieving compliance. It is so important that UK companies have easy access to labs that offer a wide range of microbiological testing, including the new EN 17272 standard.
