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PAS 2424: 2015
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Quick understanding of the test
PAS 2424: 2015 - Quantitative Surface Test for Antimicrobial Efficacy of Disinfectants (Bactericidal and/or Yeasticidal) on Hard Non-porous Surfaces
Application
- Pseudomonas aeruginosa (ATCC 15442)
- Staphylococcus aureus (ATCC 6538P)
- Escherichia coli (ATCC 8739)
- Candida albicans (MTCC 3017)
- A microbial suspension is inoculated onto a hard surface, followed by disinfectant application with a specified volume for a specific contact time.
- Post contact period, treated and control discs are subjected to abrasion cycles and re-contamination followed by another contact time.
- After contact time, discs are transferred to neutralizing solution, followed by microbial enumeration using plate count technique.
- The reduction in microbial count is calculated to evaluate the disinfectant’s efficacy.
- Determines the residual efficacy of the product, unlike most European standards that assess only initial antimicrobial activity.
- Simulates real-world conditions by incorporating abrasion and re-inoculation steps
Turnaround Time
Passing criteria
To pass, the product must achieve a โฅ 3-log microbial reduction, alongside a โฅ 4-log reduction when tested as per EN 13697.
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Abstract
PAS 2424 provides a standardized laboratory method to assess the residual antimicrobial efficacy of chemical disinfectants on hard, non-porous surfaces over a 24-hour period. In the market, many available antimicrobial disinfectant formulations claim to achieve 24-hour or long-lasting protection from germs. Apparently, there are no standard protocols to check such efficacy claims. PAS 2424 is a test method that checks if disinfectant formulations really have the potential to provide antimicrobial protection over a 24h contact period.
PAS 2424 test method is designed as an extension of EN 13697. While EN 13697 tests the initial antimicrobial activity of disinfectants, PAS 2424 assesses the residual antimicrobial activity of products. Products must therefore meet the minimum efficacy requirement under EN 13697 before being evaluated using PAS 2424. This ensures that only products with proven immediate efficacy are further assessed for residual performance.
PAS 2424 test standard
PAS 2424 has been formulated to work in combination with EN 13697. While PAS 2424 is used to assess the residual antimicrobial activity of products, the EN 13697 tests the initial antimicrobial activity of disinfectants. Meeting the requirements defined in PAS 2424 can ensure that a product performs well under specific abrasion cycles and exposure to microorganisms, ensuring its claims for extended protection against microorganisms. This test method is particularly effective in demonstrating the reduction in microbial contamination even after exposure for 24 hours under challenging conditions.
PAS 2424 test conditions
The test for PAS is carried out under standardized conditions in order to obtain reproducible and reliable results. It generally comprises:
- Temperature: Carried out at 20ยฐC.
- Interfering substance: To closely mimic clinical conditions, an interfering agent like 3.0 g/L bovine albumin is used.
- Contact time: Bacteria are exposed to the disinfectant for a contact time of 5 minutes, while yeasts have a contact time of 15 minutes. (The contact time can be modified depending on the manufacturerโs instructions.)
- Abrasive cycles: Abrasion cycles are used to replicate wear and re-contamination of the test surface.
PAS 2424 test requirements
Test organisms
For Bactericidal testing:
- Pseudomonas aeruginosa (ATCC 15442)
- Staphylococcus aureus (ATCC 6538P)
- Escherichia coli (ATCC 8739)
- Enterococcus hirae (ATCC 10541)
- Klebsiella pneumoniae (ATCC 4352)
- MRSA (ATCC 33591)
- Salmonella enterica (ATCC 10708)
For Yeasticidal testing:
- Candida albicans (MTCC 3017)
Passing criteria
To pass the test, the product must demonstrate โฅ3 log reduction in the microbial. Results of the PAS test shall only be considered valid if the product achieves a โฅ4 log reduction under the EN 13697 test, carried out under specified test conditions, i.e., specified contact time, temperature, and organic load.
PAS 2424 test methodology
- Preparation of test discs
Steel discs are inoculated with the recommended test microorganisms and allowed to dry.
- Product application
Application of test product: The disinfectant product under test is applied to five of the inoculated discs, additional five other discs are exposed to hard water (control). The application may use the concentrated or diluted form of the test product depending on the product’s intended use.
- Abrasion and re-contamination
The treated and control discs are subjected to three cycles of abrasion after a contact period of 24 hours to simulate the wear and re-contamination events that would occur in the practical conditions.
- Post-contact period and incubation
After 24 hours, all treated discs along with the corresponding control discs, are reinoculated with the test microorganism. An interfering substance like 3.0 g/L of bovine albumin is added to the discs and incubated under controlled conditions at 20ยฐC for the specified contact time.
- Neutralization
After incubation, the discs are transferred to a neutralizing solution, which halts the action of the disinfectant and prevents further microbial activity.
- Bacterial recovery and plate count
The neutralizing solution is analyzed using the plate count method to detect the presence of any surviving microorganisms.
- Calculation of residual efficacy
The residual antimicrobial activity is determined by comparing the difference in microbial reduction between treated discs and control discs.
Importance of PAS 2424 test
PAS 2424 fills a critical gap in market trends regarding long-lasting antimicrobial efficacy claims. Existing European standards, such as EN 1276 and EN 13697, are specifically designed to assess the immediate antimicrobial activity of a product. However, in everyday settings, whether domestic, healthcare, or institutional surfaces are rarely left untouched. They are subjected to frequent handling, wiping, and re-soiling. Therefore, claiming residual efficacy without considering these factors would be considered void.
PAS 2424 demonstrates a test method that mirrors actual usage conditions to check residual antimicrobial efficacy. By incorporating abrasion and re-inoculation steps it allows for more accurate evaluation of how long a disinfectant remains effective on a treated surface. As such, it not only supports compliance with regulatory expectations but also enhances product credibility and consumer trust. This makes PAS 2424 a vital tool for both product development and regulatory approval in the antimicrobial product space.
Strengths of PAS 2424 test standard
- Simulates real-life conditions: The use of abrasion cycles combined with microbial challenges replicate natural usage conditions in the product..
- Extended efficacy: The test confirms the extended antimicrobial efficacy (residual efficacy) of products and can support claims for 24-hour protection.
- Versatile: The standard is applicable to multiple industries from the healthcare and food-processing industry to public space, or institutions.
- Aligns with EN standards: PAS test extends the efficacy requirements set by EN 13697 and adds an additional layer of validation.
At Microbe Investigations Switzerland (MIS), we specialize in PAS 2424 testing helping you prove the long-lasting efficacy of your disinfectant products under real-world conditions. Whether you’re preparing for regulatory submission or market entry we offer the precision and expertise you need.
Additionally, we also offer disinfectant testing services that align with EPA-approved protocols such as EPA MLB SOP MB 40, EPA #01 01A, and EPA MLB SOP MB 41.
Contact us today to discuss your testing needs or request a quote for PAS 2424 test.
Frequently Asked Questions
DR. Martinoz Scholtz
PAS 2424 test is a quantitative non-porous surface test that evaluates the residual bactericidal and/or yeasticidal activity of chemical disinfectant products.
The PAS test is intended for disinfectant formulations used in homes, schools, hospitals, nursing homes, and industrial areas.
The test takes 3-4 days to complete.
At Microbe Investigations Switzerland, we perform the test using Pseudomonas aeruginosa (ATCC 15442), Escherichia coli (ATCC 8739), Staphylococcus aureus (ATCC 6538P), Enterococcus hirae (ATCC 10541), Klebsiella pneumoniae (ATCC 4352), MRSA (ATCC 33591), Salmonella enterica (ATCC 10708), Candida albicans (MTCC 3017). Additional strains can be added on request.
PAS tests are conducted at 20ยฐC with 3.0 g/L bovine albumin as an interfering substance. The contact time is 5 minutes for bacteria and 15 minutes for yeast.
PAS test is not mandatory however, it is highly recommended for products claiming long-term residual antimicrobial activity.
Industries that manufacture disinfectant products with residual antimicrobial activity benefit from this certification.
No the PAS test is applicable only to disinfectant products used on hard non-porous surfaces to assess their residual antimicrobial activity.
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