UV in hand dryers and air sterilisation units – what, why and how?
Ultra-violet lights are becoming a popular addition to hand dryers. They are also used in air sterilisers in places such as hospitals, care homes/nursing homes, food storage facilities and washrooms to rid them of bad smells and clear the air of bacteria such as Coronavirus family of viruses (as yet not tested specifically on the strain COVID19), E. coli, listeria, flu and other airborne microbes.
Wondering about the relationship between the COVID-19 and UV light? Can UV kill it? Is it safe? Wonder no further, we talked about all of this in this blog post on coronavirus and UV light.
Biozone AirCare solutions can destroy the Human Flu virus, H5N1, and Coronavirus in 0.44 seconds (5.7 Log Reduction – Source: CNRS France) – Scientific Report
There is however a difference in what the UV light is there to do in certain hand dryers and how effective they can be.
This post highlights the different uses of UV in hand dryers and introduces you to what an air steriliser is and its benefits. It also highlights some do’s and don’ts when locating one of these machines in your washroom.
* Related blog post – “Can UV kill coronavirus? – What’s Safe and What’s Not“
First of all, the blue light that shines on the hands in some hand dryers is there just for show and does not kill germs. UV is invisible and a blue light is often used to give the impression of UV, whilst the UV is in another area of the unit. This is a misconception which circulates and gives a perception that this is what it is there to do. It is really there just to look nice. However, it can be used as a guide to where the airflow is, so does have its advantages in speeding up dry times.
There are UV lights added to hand dryers to help keep the insides of the hand dryer clean. UV has been used for over 100 years to disinfect air and surfaces. Over time it breaks down the DNA of bacteria and microbes, rendering them dead. A UV light working constantly on the inside of the unit has enough time to sterilise the parts you can’t access easily or regularly.
It is important to note that these are in no way cleaning the air passed through the hand dryer. The lamps required for high velocity hand dryers would be unviable and need to be extremely large.
Common types of washroom Air Sterilisation units can clean about 20 litres of air per minute which is about 0.7 CFM. As an example, using a hand dryer which draws 64 CFM of air in with an average run time of 20 seconds, the dryer is going to require 21 CFM of sanitised air. Therefore, it would require 29.73 mins to create this much sanitised airflow in the hand dryer to blow out again! So, to think that a hand dryer can use UV to clean the air around its immediate vicinity before it’s drawn in is unrealistic.
The fans in these common types of washroom Air Sterilisation units are relatively small so they do not make too much noise, and can fit into a unit that is a convenient size and weight for a washroom fixture. The fan is there primarily to ensure the plasma is distributed onto the air stream within the treated spaced, where it is disinfected and odour reduced.
Installing an air sterilisation unit is a great addition to any washroom
Because of an air sterilisation unit’s ability to kill germs and remove bad odours, they are a perfect addition to any washroom.
How do air sterilisers work?
They use a technology which creates ultraviolet light, ozone, photoplasma, and negatively-charged ions. These substances all exist in the environment and have been proven to be powerful and effective disinfectants. They destroy odours, bacteria, viruses, mould, and mildew, and break down unwanted chemicals and compounds.
UV light and plasma are powerful enough to penetrate the cell walls of microorganisms and shatter the DNA, making it impossible for them to grow and reproduce.
These are perfectly safe to use although there are a couple of things to think about regarding safety and effectiveness.
You shouldn’t place one of these units near a room’s exhaust systems / open windows / vents, as the plasma will be vented from the room before it has a chance to treat the space.
It is advisable to install them as high up as possible, preferably on the ceiling, close to the odour source or cause of contamination. Placing the unit as high up as possible will make sure more of the air is cleansed. Plasma sinks as gravity plays its part, therefore it needs to be higher up to ensure air is deodorized as it is carried on the air currents within the room. So the higher up the room, the more chance of decontaminating a larger amount of air.
It is not advisable to have a unit to close to head level for health and safety reasons. Although the concentration of ozone in these units are at very safe levels, it is still not advised to have the unit low down in the room where the ozone can be ingested. Especially where children may be at a similar height to the unit as they can be more sensitive to the ingestion of ozone.
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