ASTM E3135-18. Standard Practice for Determining Antimicrobial Efficacy of Ultraviolet Germicidal Irradiation Against Microorganisms on Carriers with simulated Soil.
Test accredited by ENAC (Spanish National Accreditation Entity) for bactericidal, fungicidal and virucidal activities.
ASTM E3135 defines the test conditions for evaluating germicidal ultraviolet light irradiation devices (mercury vapor bulbs, light emitting diodes, or xenon arc lamps), which are designed to kill or inactivate microorganisms deposited on inanimate supports.
This standard does not recommend either test microorganisms or soiling conditions, but rather indicates that the test microorganisms and soiling conditions, if any, should be selected by the customer based on the specific objectives of the UV irradiation device performance antimicrobial assay evaluation. As an example, two soiling agents are mentioned, a hydrophilic soiling agent, artificial saliva, and a waxy hydrophobic agent, artificial sebum, but indicates that appropriate soiling conditions should be chosen for the actual application of the irradiation device. The ASTM E3135 standard also indicates that the assay can be performed without using any interference substance. Depending on the application area of the equipment, the customer can order the use of other interferences substances indicated by the EN or BPR guidelines (as example, bovine serum albumin 3 g/L; bovine serum albumin 0.3 g/L; bovine serum albumin 3 g/L + erythrocytes 3 mL/L; or bovine serum albumin 10 g/L + yeast extract 10 g/L).
The test described by the ASTM E3135 standard is performed on 2.5 cm diameter carriers of any material representative of the type of surface to which the UV irradiation device will be destined in its actual use. To carry out the test, 6 carriers are used per test microorganism and selected soiling condition (no soiling, with hydrophilic soil, waxy soil or other soiling conditions indicated by the customer). The test microorganism is deposited on each carrier and, if necessary, once the inoculum has dried, the soiling agent is added. Of the 6 carriers, 3 carriers will be exposed to the UV light source in accordance with the instructions on the irradiation device label and must simulate actual use of the device. At the same time, the three remaining carriers, used as controls, are incubated at room temperature without UV treatment. At the end of the exposure period, the microorganisms are removed from the carriers and the number of existing surviving microorganisms is quantified, by culture in appropriate media for bacteria and fungi, or by titration in cell cultures appropriate for viruses. With these counts, the percentage reduction for the test microorganism due to UV treatment under a specific soiling condition is calculated by comparing the average of the viable microorganisms recovered from the untreated control carriers with the average of the viable microorganisms recovered from the UV-treated carriers.
In our laboratory, these tests are carried out in a 74 m3 chamber. In general, at IVAMI these tests are performed on stainless steel carriers, if the client wishes to carry out the test on another type of carrier, to adapt it to the conditions of use of their device, they can consult us or provide us with the test carriers. This test is usually performed to test UV irradiation device efficacy against bacteria, yeast, fungi and viruses indicated below. If you need to perform the test with another microorganisms or viruses, consult us. The customer must indicate the irradiation procedure to follow with his product (irradiation time, distance from the UV source to the test supports, the relative angle of exposure to ultraviolet light, and the position of the supports relative to the length of the device) and the test conditions (test microorganisms, dirt conditions to be used, the material of which the test supports must be made, initial test temperature, and initial relative humidity range). Due to the opening hours of our Center, the irradiation time of the tests must be equal to or less than 8 hours, or equal to or greater than 15 hours.