Fully accept­ing his bias, Paul Revere looks at the evi­dence in the long-standing paper towel–hand drier debate and finds in favour of the hum­ble paper towel.

There were four parts to the study: Part A looked at the dry­ing effi­ciency of hand dry­ing method; Part B involved count­ing the num­ber of dif­fer­ent types of bac­te­ria on the hands before and after dry­ing; Part C stud­ied the poten­tial con­t­a­m­i­na­tion of other users and the wash­room envi­ron­ment; and Part D took a bac­te­r­ial sam­pling of Dyson Air­blade dry­ers in pub­lic washrooms.

Paper tow­els and the Dyson Air­blade were found to be equally effi­cient at dry­ing hands, each achiev­ing 90% dry­ness in approx­i­mately 10sec. How­ever, the warm air dryer was con­sid­er­ably less effi­cient, tak­ing 47sec to achieve the same level of dryness. […]

Paper tow­els were found to reduce the num­ber of all types of bac­te­ria on the fin­ger­pads by up to 76% and on the palms by up to 77%. By com­par­i­son, the Dyson Air­blade increased the num­bers of most types of bac­te­ria on the fin­ger­pads by 42% and on the palms by 15%. How­ever, after wash­ing and dry­ing hands under the warm air dryer, the total num­ber of bac­te­ria increased by 194% on the fin­ger­pads and on the palms by 254%.

The Dyson Air­blade per­formed less well than paper tow­els and the warm air dryer in Part C in which the hands of 10 sub­jects were arti­fi­cially con­t­a­m­i­nated with yeast sus­pen­sion. Dur­ing use, open agar plates were placed at 0.25m inter­vals from the hand-drying device up to a max­i­mum of 2m. Yeast colonies that grew on the plates were counted.

The Dyson Air­blade dis­persed poten­tial con­t­a­m­i­na­tion to other users and the wash­room envi­ron­ment to a dis­tance of at least two metres, whereas paper tow­els spread con­t­a­m­i­na­tion 0.50m and the warm air dryer 0.25m.

Part D showed that the Dyson Air­blade dry­ers in the pub­lic wash­room sam­pled were con­t­a­m­i­nated with large num­bers of bac­te­ria, includ­ing poten­tial pathogens such as E. coli, staphy­lo­coc­cus and pseudomonas aerug­i­nosa, par­tic­u­larly the bot­tom of the hand dry­ing chamber

Accord­ing to Keith Red­way, senior aca­d­e­mic in the depart­ment of Bio­med­ical Sci­ences at the Uni­ver­sity of West­min­ster: “The results of all parts of this study sug­gest that the use of warm air dry­ers and jet air dry­ers should be care­fully con­sid­ered in loca­tions where hygiene is of para­mount impor­tance, such as hos­pi­tals, clin­ics, kitchens and other food prepa­ra­tion areas, schools, nurs­eries and care homes.” (Clean Room Tech­nol­ogy [UK])

I have odd hand wash­ing habits in pub­lic bath­rooms and have my own preferences:

  • Paper tow­els pre­ferred if there are doors to open on exit­ing the bath­room. This is because many users of pub­lic bath­rooms do not wash their hands, and I don’t want to re-contaminate my hands after wash­ing and drying–I’ll use a paper towel to open the door.
  • The Dyson Air­blade in all other circumstances.

Odd habits, admit­tedly, and habits that are unlikely to change given these find­ings… mainly because the research was funded by the Euro­pean Tis­sue Sym­po­sium.

via Mar­ginal Revolution