Hand Dryers: How They Can Spread Bacteria in Public Toilets

It sounds ridiculous, yet it is real.

In public toilets, electric hand dryers are often seen as a modern, sustainable option. They create no paper waste, need no refilling and frequently have an elegant design. However, an experiment by a scientist indicates that these very machines can secretly spread bacteria – turning supposedly clean hands into a microbial trap again.

What a simple laboratory experiment reveals about hand dryers

The researcher, known online as “Devon Science”, wanted to find out exactly how many bacteria can actually land on us when we hold our hands beneath a dryer in a public toilet.

She used an item found in any school laboratory: Petri dishes containing growth medium. One dish was placed directly beneath a running hand dryer. A second remained in the laboratory, exposed only to the comparatively clean air in the room, to serve as a control.

By the following day, the contrast was difficult to miss. The laboratory dish was largely clear, whereas the dish from the toilet was covered in yellow, black and white colonies. Each spot represented millions of bacteria blasted on to the growth medium by the dryer’s airflow.

The experiment suggests that hand dryers blow out not only air, but also concentrated clouds of germs from the toilet directly on to the skin and into the face.

Which germs may be present in hand dryer air

The colonies that developed were not merely harmless “microbial background noise”. They also included organisms that matter in medical settings:

• Staphylococcus aureus: a bacterium that can cause spots, boils and wound infections, among other conditions – and, in unfavourable circumstances, pneumonia as well.
• Escherichia coli (E. coli): a typical inhabitant of the gut, often found in traces around toilet areas. Certain strains can trigger diarrhoea, urinary tract infections and more serious illnesses.
• Fungal spores: black dots indicate fungi, which can become particularly problematic for people with allergies or weakened immune systems.

The precise mixture will naturally vary from one toilet to another. Yet the overall picture is clear: the airflow from the machine picks up a broad range of microorganisms from its surroundings and redistributes them.

Why hand dryers spread germs so effectively

The key factor is the technology inside the unit. Modern high-performance machines advertise exceptionally fast drying, achieved through air delivered at high pressure and tremendous speed.

• High air speed: some models produce airflow equivalent to several hundred kilometres per hour. This can dislodge microdroplets of water, dirt and faecal germs from numerous surfaces in the washroom.
• Aerosols everywhere: every flush from an open toilet sends microscopic droplets into the air. These droplets often contain gut bacteria. The hand dryer picks up these aerosols and stirs them up again – only in a far more concentrated form.
• Contamination inside the appliance: in a further stage of the experiment, the researcher swabbed the interior of the dryer. The swab turned dark, providing a clear sign of accumulated deposits. This is exactly where the air intake is located.

Once activated, the dryer draws in these particles, combines them with the room air and propels them back out in a powerful stream – directly into the breathing zone and on to skin that is still damp.

Why damp hands are an ideal target

For microorganisms, moisture is effectively a welcome sign. Wet skin provides bacteria and fungi with ideal conditions for sticking and spreading. If a dryer blows germs on to hands that remain slightly damp, it improves their chances of becoming established there.

Anyone who washes their hands and then holds them beneath a heavily contaminated hand dryer may, in the worst case, pick up more bacteria than were previously on their skin.

Are modern hand dryers with HEPA filters genuinely safe?

Manufacturers have responded to criticism in recent years by promoting technical systems intended to “clean” the airflow. Two terms appear especially often: HEPA filters and UV light.

• HEPA filters: this filter class can theoretically remove around 99.97 per cent of particles down to a particular size from the air. They are standard in high-quality air purifiers and operating theatres. So far, only some hand dryers contain them – and even in those units, their effectiveness depends entirely on regular servicing and prompt replacement.
• UV irradiation: some newer models route air past UV lamps designed to damage bacteria. The method works in laboratory conditions, but its real-world effectiveness depends on how long the air remains exposed, the lamp output and correct positioning.

One important point remains: many older or cheaper dryers have neither an effective HEPA filter nor UV technology. Even with high-end units, the washroom air and its aerosols remain a concern.

Responses from healthcare workers and users

The viral experiment prompted international debate, including among nurses and doctors. Employees of state healthcare systems spoke up to question whether hand dryers are genuinely appropriate in hospitals, doctors’ surgeries and care homes – especially in places used by vulnerable people.

In everyday life, many users react more instinctively. Some say they will return to using paper towels or shake their hands dry rather than switch on a dryer. Others point out that certain facilities have already moved to paper towels because studies have produced similar findings for years.

The fundamental question is: do we want to use technology that actively blows germs around the room in sensitive settings?

Which option performs better in direct comparisons

Several studies, including research independent of the TikTok experiment, reach a recurring conclusion: paper towels usually perform better than air dryers in hygiene terms. The reason is straightforward: drying with paper mechanically removes some microorganisms from the skin rather than redistributing them.

The options can broadly be compared as follows:

Method	Hygiene aspect	Typical problems
Paper towels	Reduce germs through rubbing, with no airflow	Waste, the need for refills, and no alternative when the dispenser is empty
Warm-air dryers (older models)	Long drying time creates more opportunity for germ transfer	Stirring up aerosols, often no filter, and infrequent cleaning
High-speed hand dryers	Fast drying, sometimes with filters	Extremely powerful airflow and the spread of microdroplets throughout the room

Practical advice for travel and office use

Anyone who now sees clouds of germs during every washroom visit does not need to panic. A few straightforward habits can noticeably reduce the risk:

• Wash hands for long enough: use soap for at least 20 seconds, remembering the spaces between fingers and the thumbs. Good hand hygiene before drying remains the most important step.
• Use paper where possible: when a washroom provides both a dryer and paper, paper is usually the option with fewer germs.
• Avoid dryers that are visibly dirty: dusty or stained air inlets and outlets rarely indicate good maintenance standards.
• Shake hands briefly in the air: where there is no alternative, slightly damp hands may feel unpleasant but could carry fewer foreign germs than hands that have just been “blown dry”.
• Do not hold your face directly in the airflow: taking a small step back reduces the number of droplets that reach the mouth and nose directly.

Why toilet aerosols are an underestimated issue

The source of the problem is not the dryer alone, but the wider environment. Every flush from an open toilet creates a kind of invisible fountain of microdroplets. Studies have shown that these droplets can still be detected several metres away, particularly in cramped, poorly ventilated washrooms.

These aerosols contain bacteria and viruses from faeces, urine and respiratory secretions. The hand dryer then acts as an amplifier: it collects what is already suspended in the air and blows it forcefully towards one concentrated area.

Background: what HEPA, germs and colonies actually mean

A brief look at the terms that repeatedly arise in this debate makes the issue clearer. “HEPA” describes a filter class capable of removing extremely fine particles from the air. Such filters consist of a dense mesh of fibres that traps dirt, pollen, bacteria and, in some cases, viruses. However, they require regular replacement; otherwise, they can become a source of germs themselves.

When specialists refer to “colonies” on a Petri dish, they mean visible clusters of bacteria that developed from one or a small number of original germs. The colourful growth on the dish from the hand dryer experiment illustrates how many different types were present and how effectively they can multiply on a suitable surface.

What operators of public buildings can do now

Schools, shopping centres, businesses and hospitality venues face a very practical question: which solution best suits their hygiene standards, budget and environmental considerations? There is no universal answer, but several guidelines are emerging:

• In sensitive settings such as clinics and care homes, paper towels are currently the safer option.
• Where hand dryers are essential, modern units with tested filters should be installed and maintained rigorously.
• Good ventilation and closing toilet lids before flushing noticeably reduce the amount of aerosols in the room.

The experiment by “Devon Science” does not show that every hand dryer automatically makes people ill. It does, however, draw attention to a hygiene issue that can easily hide behind stainless steel and hot air. Anyone faced with the choice in a washroom may now view the loud airflow rather differently.