The Hjelt Institute of Hygiene and Microbiology (University of Helsinki) studied the effectiveness of four common hand-drying systems in terms of hand hygiene.
The results of the study are clear:
- Cotton towels have proven more effective in reducing bacteria through the drying process than the two air dryers included in the study;
- Cotton and paper towels eliminate the highest number of bacteria from wet hands;
- The mechanical action of rubbing one´s hands with cotton or paper contributes to the effective removal of bacteria;
- Good hand hygiene involves both washing and drying hands.
Cotton towels remove more bacteria from your hands than air dryers
The performance of cotton towels in removing bacteria from hands is over and above the minimum requirement set by the European hand washing standard EN 1499. The performance of jet and warm air dryers, however, did not meet the European standard requirements.
The baseline measurement is the level of bacteria on the hands after they were contaminated and before they were dried.
Cotton removes more bacteria from hands than jet air and warm air dryers:
- Hands dried with cotton show a log reduction of 4.41;
- Hands dried with paper show a log reduction of 4.41;
- Hands dried with jet air show a log reduction of 2.48;
- Hands dried with warm air show a log reduction of 1.79
- Air dryers do not meet the minimum requirements of the European standard;
- Cotton performs over and above the European standard minimum
requirements and is therefore a more hygienic hand drying solution.
Proper hand drying is essential to hand hygiene
Hand hygiene is the single most important measure to reduce the burden of healthcare-associated infections.
Crucially, as the transmission of bacteria is more likely to occur from wet skin than from dry skin, the proper drying of hands after washing is an essential component of hand hygiene. Wet hands that touch a surface will contaminate a clean surface - or be contaminated by a dirty one - more quickly than properly dried hands.
Therefore, once effectively dried, the risk of re-contamination of hands is hugely reduced.
- Some facts about hand hygiene
In everyday life, however, we know that:
- Only 5% of people using washrooms wash their hands long enough to kill the germs that cause infections*;
- 33% of people do not use soap due to its drying effect on the skin*;
- 10% of people don't wash their hands at all*.
*Source: Borchgrevink et al. 2013, Journal of Environmental Health
Cotton towel dispensers have very hygienic surfaces
The surfaces of cotton towel dispensers carry significantly less risk of contamination for wet hands than the surfaces of jet air dryers.
- The jet air dryer is the only device which showed heavy contamination, including E-coli, with a particularly heavy concentration at the inside bottom of the dryer (Fig. 1);
- A small number of bacteria were found on the warm air dryer, where it is most likely to be touched by wet hands;
- A small number of bacteria were found on the paper dispenser, where it is most likely to be touched by wet hands;
- An insignificant amount of bacteria was found on the cotton towel dispenser..
- Read more on the contamination of dryer surface
- When testing the contamination of the surfaces of the four drying methods, the most commonly touched parts of each dispenser or dryer were swabbed (Fig. 2):
The study was carried out according to the European standard EN 1499: Chemical disinfectants and antiseptics - Hygienic handwash - Test method and requirements (phase 2/step2), April 2013.
Test devices used:
- Cotton towel dispenser ('CWS Paradise Dry Slim'), with slim white hand towel, 100% cotton, 32 cm portion
- Paper dispenser ('Easy Cut Electronic'), with virgin Grite 1 ply 40gr/m2, 100% pure pulp paper
- Warm air dryer ('DAN Air Dryer')
- Jet air dryer ('Dyson Airblade')
Cotton towels lead to a better air quality
Cotton towels lead to a better air quality in the washroom than air dryers.
- Read more on bacteria in the air
Tests to quantify the number of bacteria in the air in the vicinity of the air dryers show the following crosscontamination effect:
- within 1m of the jet air dryer, a significant amount of bacteria was found in the air, including E-coli;
- the air in the washroom can still be highly contaminated by aerosol up to 2m distance from the air dryers;
- bacteria were quasi non-existent in the air surrounding the cotton and paper dispensers at a distance of 1m or 2m.
- It would appear that bacteria are dispersed via the air stream of air dryers and that this leads to contamination of the surrounding air. This phenomenon was not found with cotton and paper towels.
- Limiting the spread of pathogenic microbes is particularly important in healthcare environments.
- The use of cotton towels leads to a better air quality than the use of air dryers in the washroom.
Hjelt Institute of Hygiene and Microbiology of the University of Helsinki Report
The contents of this page are based on the Comparative study of four drying methods: cotton towels, paper towels, jet air dryer and warm air dryer - A research report of the Hjelt Institute of Hygiene and Microbiology of the University of Helsinki. Kirsi Laitinen, PhD.