Disinfection of rooms by fogging
On the biocidal products market, we can observe an increase in interest in preparations for disinfecting rooms by fogging. The increasing popularity of this disinfection method is directly related to the issuance of the standard: 17272:2020-10 by the European Committee for Standardization. The current SARS-CoV-2 epidemic also contributed to the popularization of “fogging”. Public awareness of the need to keep rooms clean and sterile is also increasing. This is particularly important from the point of view of health care facilities, teaching facilities, collective accommodation complexes, as well as the broadly understood veterinary area (including livestock buildings and procedures related to animal transport). Specialized laboratories offer these tests and provide assistance in selecting the research scope.
What is room disinfection by fogging?
Disinfection of rooms in an automatic process, also called fogging, involves spraying a disinfectant in the form of steam, aerosol or gas. The preparation is most often dispersed using a specially adapted device whose task is to administer the appropriate dose of disinfectant per unit of time. However, this is not the rule. Manufacturers of chemical disinfectants are trying to eliminate the use of additional equipment. They work on single-use products or devices that spray an aerosol under pressure directly from the container containing the preparation. Disinfection by fogging is a much more effective process than standard methods based on, for example, spraying the surface. The aerosol produced in this way is able to reach all places in the room and significantly minimizes the risk of damaging surfaces or equipment (e.g. medical), for which too much spraying of the disinfectant could be harmful. Human involvement is also reduced due to process automation.
Test procedure
Preliminary test
A distribution test, also known as a “preliminary test”, assesses the performance of a device in a test room. Depending on the purpose of use, the standard allows the test to be carried out in rooms up to 4 m³ (small rooms). The actual test is carried out in rooms ranging from 30 to 150 m³ (large rooms). The distribution test should be performed under identical conditions to those used during the efficacy test. Regardless of the research scope chosen by the Client, the test strain should be Staphylococcus aureus. Reduction of the pathogen by at least 5 logarithms allows the methodology to be considered validated. After achieving the required degree of reduction, you should proceed to the second stage, i.e. the actual test.
Efficacy test)
The efficiency test, to put it simply, involves placing test plates covered with a suspension containing a standard organism at appropriate distances from the emitter. The arrangement of test strains must meet the requirements strictly specified in the EN 17272 methodology. Appropriate placement of test strains enables the assessment of the effectiveness of fogging in the tested chamber. The next step is to spray the disinfectant in accordance with the instructions of the manufacturer of the device supplied for testing. The task of the “fogger” is to fill the entire volume of the room with gas. The effectiveness of the device is, of course, also influenced by the disinfectant used in the process. A very important element is the synergy between the device and the biocidal preparation. It not only enables disinfection efficiency, speeds up the process, but also saves on the chemicals used. The disinfection process usually takes from several minutes to several hours. After completing the disinfection process, laboratory technicians carry out tests and calculate the degree of reduction of a given pathogen in relation to the requirements of the standard. Finally, a comprehensive research report is prepared.
Biocidal preparations used in the fogging method
Chemical disinfectants used for fogging are usually designed so that their harm to the user and the disinfected surfaces is as low as possible. An important element is also the ease of airing the rooms after the process. The most frequently used active substances are hydrogen peroxide and compounds from the group of quaternary ammonium salts (e.g. benzalkonium chlorides). Compounds based on sodium hypochlorite or hypochlorous acid are also popular. The latter is becoming more and more popular among producers of biocidal products, as well as their recipients. Alcohol as an active substance in disinfection with this method is much less common.
Selection of the research scope
The PN-EN 17272 standard enables the assessment of biocidal effectiveness against bacteria, fungi, viruses, mycobacteria, spores, and bacteriophages. The choice of the research scope depends on the client’s requirements and the area of application in which we intend to operate. In order to meet the requirements of the methodology, tests should be carried out confirming at least bactericidal and yeasticidal activity. Disinfection by fogging is used in medical, veterinary, domestic, as well as industrial and institutional areas (groups 2, 3 and 4 of category 1). The method was developed on the basis of the French standard AFNOR NF T72 281, which was replaced by a younger equivalent in 2020.
Reference strains
Group II Medical area
In group II, category I of the classification of Annex V to the Biocidal Products Regulation, we list preparations used in the medical area and outside the medical area. In the case of confirming the bactericidal effectiveness in both situations, the basic test strains are P.aeruginosa, S.aureus, E.coli K12 and E.hirae. Additionally, the Manufacturer may decide to carry out tests, including: in terms of Salmonella and Legionella bacterial strains or in the context of disinfection at temperatures >40 degrees Celsius for: E.faecium. The fungicidal effectiveness in PT2 is confirmed on C.albicans and A.brasiliensis strains, the sporicidal effectiveness on B.subtilis, the tuberculocidal effectiveness on M.terrae and M.avium, and the virucidal effectiveness to the extent consistent with the declarations that the product should meet. Model viruses may be: Feline calicivirus, Poliovirus type 1, Murine norovirus, Adenovirus type 5, Rotavirus, Vaccinia Virus, Human coronavirus 229E, influenza viruses and others. The use of disinfection at temperatures >40 degrees Celsius requires tests confirming effectiveness against the Murine Parvovirus strain.
Group III Veterinary area
In this group, we test the bactericidal effectiveness with the following strains: P.aeruginosa, S.aureus, E.coli K12 and E.hirae. We consult any optional strains directly with the entity ordering the test, depending on the needs. The strains of fungi are: C.albicans and A.brasiliensis, spores: B.subtilis and additionally B.cereus, mycobacteria: M.terrae, and the reference virus is: Bovine Enterovirus (BEV).
Group IV Area of food and feed production
The last product group in which fogging devices are used is group IV, i.e. food and feed. In PT4, we confirm bactericidal, fungicidal, sporicidal and virucidal effectiveness on the same pathogens as in group II. The exception is tuberculocidal effectiveness, which is not required to be confirmed. In the case of group IV, phagecidal activity can be additionally determined. Selected strains of phages are used to destroy pathogenic bacteria. The bacteria used to assess phagecidal activity are most often Lactobacillus lactis P001 and Lactobacillus lactis P008.
Microbial reduction requirements in efficacy testing
We confirm the bactericidal effectiveness when we achieve a reduction level of ≥5 log, and this applies to both the preliminary test and the actual test. Confirmation of fungicidal, tuberculocidal, virucidal and phagecidal activity is obtained by obtaining a logarithm of ≥4. The exception are the requirements for disputes, where in PT2 of the medical area it is necessary to achieve a reduction above 4 logarithms. However, in the industrial, domestic and institutional areas (PT2 except for the medical area), as well as in the veterinary (PT3) and food (PT4) areas, this requirement is ≥3 log.
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