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EN 13623

Evaluate Bactericidal Activity of Chemical Disinfectants against Legionella

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BS EN 13623 : 2020 – Quantitative suspension test for evaluation of bactericidal activity against Legionella for aqueous systems (phase 2, step 1)

EN 13623 is designed for chemical disinfectants/antiseptics intended to be used in aqueous systems to eliminate Legionella pneumophila.

EN 13623 standard is applicable to products formulated for one time shock treatment to kill Legionella pneumophila. This method is suitable for disinfection of water in cooling towers, spas, pools, showers and other similar applications.

However, EN 13623 is not a method of choice for the evaluation of products that are consistently used in water systems to prevent the growth of Legionella pneumophila.

EN 13623 Test Conditions & Requirements


Obligatory test conditions


Bactericidal activity in water for general purposes

Bactericidal activity in cooling water

Additional test conditions

Test organisms

Legionella pneumophila

Legionella pneumophila

Other strains and species of Legionella can be used

Test temperature

20 °C

30 °C

No other temperatures are considered relevant to this test

Interfering substances

0,000 5 % yeast extract

0,000 5 % yeast extract


Contact time 

60 min ( for rapid acting products)


15 h (for slower acting products)

60 min (for rapid acting products)


15 h (for slower acting products)

2 h, 6 h, 15 h, 40 h, 48 h


Hard water

Buffered ferrous hard water


Test Process of EN 13623

EN 13623 Test Method

  • Product sample is diluted with either hard water or buffered ferrous hard water as per test requirements.
  • Diluted product samples are added into the test suspension of bacteria and interfering substance.
  • The mixture is maintained at mandatory time and temperature conditions explained in table above.
  • At the end of the contact time, an aliquot of solution is immediately neutralized to stop further reaction of the sample product.
  • The preferred technique is dilution-neutralization. However, if an appropriate neutralizer is unavailable, membrane filtration can be employed instead. 
  • In the next step, the recovered solution is plated and incubated to enumerate the number of viable microorganisms. 
  • Product sample must demonstrate 4 log reduction values to meet bactericidal efficacy passing criteria outlined by EN 13623. 

Importance of EN 13623 Test

Legionella outbreaks pose a significant public concern that demands urgent attention and concrete preventive measures. Such outbreaks are mainly caused by contaminated water within the water and sanitary ware systems.

This does necessitate the need for proper maintenance, disinfection, and monitoring of water systems. To effectively combat Legionella colonization in water systems, it is crucial to employ disinfectants that demonstrate bactericidal activity against Legionella pneumophila. EN 13623 outlines test requirements and performance criteria for such disinfectants to ensure their efficacy for intended use.

At MIS, we specialize in offering anti-bacterial efficacy testing services for disinfectants and materials which are designed to be used in sanitary ware and water systems to kill Legionella pneumophila.

We are a team of highly experienced professionals who render EN 13623 efficacy testing services in accordance with international standards while also prioritizing the unique requirements of our customers. Additionally, we do have facilities to perform fungicidal or yeasticidal efficacy testing services using EN 13624 standard.

Our constant focus is to consistently deliver reliable and responsive services to our esteemed clients. To get a quote on EN 13623 testing services or want to know more about our services, connect with our experts today.


EN 13623 is a phase 2, step 1 suspension test for antiseptics and chemical disinfectants planned to be used in water systems against Legionella pneumophila. To meet the efficacy criteria of EN 13623 test, the test product must kill microbes to a value of 4 log reduction.

EN 13623 test is applicable to disinfectants/antiseptic products possessing bactericidal activity against Legionella  pneumophila. This standard is performed on products used for disinfecting water in cooling towers and other artificial water systems like spas, pools, showers, and more.

EN 13623 test takes 2-3 weeks to complete.

At Microbe Investigations, we test for EN 13623 using the following strains: Legionella spp. (ATCC – 700511).

Contact us for more information

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