Hand Dryers: How Public Toilet Germs Spread Through Airflow

It sounds absurd, but it is real.

In public toilets, electric hand dryers are often seen as a modern, sustainable option. There is no paper waste, no need to restock dispensers and the units frequently have a sleek appearance. Yet an experiment by a scientist suggests that these very devices can become covert bacteria spreaders – quickly turning supposedly clean hands into a germ trap.

What a simple laboratory experiment reveals about hand dryers

The researcher, who uses the name “Devon Science” online, wanted a precise answer: how many bacteria actually end up on us when we place our hands beneath a dryer in a public toilet?

To test this, she used equipment found in any school laboratory: Petri dishes containing growth medium. She positioned one dish directly below a working hand dryer. A second dish remained in the laboratory, exposed only to the relatively clean air in the room, as a control.

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

The experiment suggests that hand dryers do not simply blow air: they send concentrated clouds of germs from the toilet environment straight on to skin and into faces.

Which germs may be present in hand dryer air

The colonies that grew were not merely harmless “background microbes”. Organisms also appeared that matter in clinical settings:

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

The exact mix will naturally vary from one toilet to another. However, the overall picture is clear: the device’s airflow picks up a broad range of microorganisms from its surroundings and redistributes them.

Why hand dryers spread germs so effectively

The technology inside the unit is crucial. Modern high-performance dryers advertise exceptionally rapid drying, achieved through high-pressure air travelling at enormous speed.

• High air speed: some models generate airflow equivalent to several hundred kilometres per hour. This can dislodge tiny droplets of water, dirt and faecal germs from many surfaces around the washroom.
• Aerosols throughout the room: every flush from an open toilet sends microdroplets into the air. These droplets often contain gut bacteria. A hand dryer captures these aerosols and stirs them up again – but in a much more concentrated form.
• Contamination inside the machine: in a further part of the experiment, the researcher swabbed the inside of the dryer. The swab turned dark, providing a clear sign of accumulated deposits. This is precisely where the air intake is located.

Once switched on, the dryer draws in these particles, combines them with the room air and fires them back out in a powerful jet – directly into the breathing zone and on to still-damp skin.

Why damp hands are an ideal target

Moisture is effectively a welcome sign for microorganisms. Wet skin provides bacteria and fungi with ideal conditions in which to cling on and spread. If a dryer blows germs on to hands that are still slightly damp, it improves their chances of becoming established there.

Someone 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?

For several years, manufacturers have responded to criticism by promoting technical measures intended to “clean” the airflow. Two terms appear especially often: HEPA filters and UV light.

• HEPA filters: in theory, this class of filter can remove around 99.97 per cent of particles down to a specified 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 maintenance and timely replacement.
• UV irradiation: some newer models channel air past UV lamps intended 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.

An important point is that many older or cheaper dryers have neither an effective HEPA filter nor UV technology. Even with high-end devices, aerosols in the washroom air remain an issue.

Responses from healthcare professionals and users

The viral experiment prompted international debate, including among nurses and doctors. Employees of state healthcare systems spoke out, questioning whether hand dryers are truly appropriate in hospitals, GP surgeries and care homes – particularly in places used by vulnerable people.

In everyday life, many users respond more instinctively. Some say they will return to using paper towels or shake their hands dry instead of switching on the dryer. Others note that some facilities have already moved to paper because studies have produced similar findings for years.

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

What performs better in a direct comparison

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

Broadly, the options compare as follows:

Practical everyday tips for travel and the office

Anyone who now sees clouds of germs every time they visit a washroom does not need to panic. A few simple habits can noticeably lower the risk:

• Wash hands for long enough: use soap for at least 20 seconds, remembering the spaces between the fingers and the thumbs. Proper hand hygiene before drying remains the most important step.
• Use paper where possible: if a washroom offers both a dryer and paper towels, paper is usually the option with fewer germs.
• Avoid a dryer if it is visibly dirty: dusty or stained air inlets and outlets rarely indicate good maintenance.
• Briefly shake hands dry in the air: where there is no alternative, slightly damp hands may feel unpleasant, but they may carry fewer outside 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 reaching the mouth and nose directly.

Why toilet aerosols are an underestimated issue

The root of the problem is not the dryer alone, but the entire environment. Every flush from an open toilet produces a kind of invisible fountain of microdroplets. Studies have shown that these droplets can still be detected several metres away, especially in cramped washrooms with poor ventilation.

Bacteria and viruses from faeces, urine and respiratory secretions can be present in these aerosols. The hand dryer then acts like an amplifier: it gathers what is already floating in the air and blows it forcefully towards one concentrated area.

Background: what HEPA, germs and colonies actually mean

A brief look at terms that constantly arise in this debate clarifies some of the issues. “HEPA” refers to a filter category capable of removing extremely fine particles from the air. Such filters are made from a dense mesh of fibres that trap dirt, pollen, bacteria and, in some cases, viruses. However, they must be replaced regularly or they can become a source of germs themselves.

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

What public building operators can do now

For schools, shopping centres, businesses and hospitality venues, the question is highly practical: which solution meets hygiene expectations, budget requirements and environmental considerations? There is no universal answer, but several guidelines are emerging:

• In sensitive settings such as hospitals and care homes, paper towels are currently the safer option.
• Where hand dryers are essential, modern units with tested filters should be installed and rigorously maintained.
• 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. But it draws attention to a hygiene problem that is easily hidden behind stainless steel and hot air. Anyone faced with the choice in a washroom in future may see that noisy airflow differently.