Automotive air conditioning systems (HVAC systems)

Case study

Improving the hygiene of automotive air conditioning systems (HVAC systems)

Heating and ventilation systems in automotive vehicles are prone to microbial contamination because the air they circulate is itself contaminated with airborne microbes. The undesirable aspects of microbes contaminating automotive air circulation systems include a persistent unpleasant odour in the cabin and the introduction of harmful microbes into the driver’s/passengers’ environment.

Antimicrobial technology serves as a solution to these issues by inhibiting the presence and survival of microbes in automotive heating and ventilation systems. Antimicrobial substances have been recognised for many years whilst recent advances in technology have allowed antimicrobial substances to be stably incorporated into polymers and coatings in order to provide an effective and lasting antimicrobial effect. (The stability of the treated material is known to allow the antimicrobial performance to be maintained for the working lifetime of automotive heating and ventilation systems)

Plastics and other non-porous surfaces, such as coatings containing BioCote antimicrobial technology has been challenged with microbes isolated from automotive heating and ventilation systems in order to measure its effectiveness at killing these undesirable organisms. BioCote antimicrobial technology is provided to manufacturers, compounders or fabricators of a wide range of products as an uncomplicated additive to be incorporated into or onto a product during normal manufacturing processes like plastic molding and coating.

The additives used in this study are based on ionic silver (silver ions) in the form of a powder and pellet and have been optimised for use in wet coatings and in parts molded in a variety of polymers.

A standard laboratory test will provide a measurement of a treated product’s antimicrobial performance. BioCote Ltd, the supplier of market-leading antimicrobial technology, has measured the performance of its technology after its incorporation into coatings simulating automotive heating and ventilation systems. The laboratory findings were unequivocal with reductions greater than 98.0% (> 98.0%) for all of the microbes used as part of the study, namely Staphylococcus aureus, Escherichia coli, Ralstonia pickettii, Sphingomonas paucimobilis, Methylobacterium mesophilicum and Chelatococcus asaccharovorans.

The microbes included in the study had been isolated from automotive heating and ventilation systems or were chosen as representatives of wider microbial groups. The method employed by the laboratory was ISO22196:2011, a reliable, quantitative test for antimicrobial surfaces. The results were as follows:

Test Surface DescriptionBacteriumNo. of microbes
START of the test
No. of microbes
END of the test
% reduction of microbes
BioCote-treated Polymers and CoatingsStaphylococcus aureus4.05E+051.11E+01>99.99%
Escherichia coli4.22E+041.11E+01>99.97%
Sphingomonas paucimobilis1.98E+046.67E+0296.63%
Methylobacterium mesophilicum3.00E+056.67E+01>99.99%
Ralstonia pickettii4.00E+051.11E+01>99.99%
Chelatococcus asaccharovorans6.50E+051.11E+01>99.99%

Laboratory test data have repeatedly revealed that BioCote antimicrobial technology is highly efficacious against the bacteria S. aureus and E coli. These bacteria are of interest because they represent wider ranges of microbes that are impractical to test.

Of particular interest to this study was the performance of the technology against the microbes known to contaminate automotive heating and ventilation systems, i.e. Sphingomonas paucimobilis, Methylobacterium mesophilicum, Ralstonia pickettii and Chelatococcus asaccharovorans.

The results strongly suggest that automotive heating and ventilation systems treated with BioCote technology will inhibit microbial contamination and reduce its undesirable effects in the cabin and maintain the long term performance of the system.

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