It is widely recognised and agreed that UVC is the type of UV light that is the most effective in destroying viruses and bacteria. When exposed for a long enough time, a pathogen is torn apart by the UVC at a molecular level, preventing it from completing the processes it needs to in order to survive.

Not all UV air purifiers are created equal

Lots of products featuring UV lamps will make ‘purifying’ claims. Certainly, the entire UV spectrum has some capacity to kill or inactivate species of microorganism. This isn’t to suggest the entire UV spectrum has a blanket effect on germs and bacteria. In fact, there are many variables when it comes to the germicide capacity of UV lamps – which is why you need to have your wits about you when selecting a UV ‘purifier’.

Really, it’s only UVC that has the capacity to fully sterilise the air. The frequency of UVC light alters the structure and the molecular bonds of microorganisms’ DNA. DNA is, in essence, a “blueprint” viruses and bacteria use to develop, function and reproduce. By destroying the organism’s ability to replicate itself, it is rendered harmless. After UVC exposure, the organism dies off leaving no offspring and the population of the microorganism diminishes rapidly. This is the case for all viruses and bacteria, including COVID-19.

However, passing air through a UVC lamp doesn’t automatically mean that it is totally sterilized. One of the most important factors is the dwell time, which we’ll begin with here. Then, we’ll move on to other things you need to bear in mind before purchasing your unit, namely, ozone production.

The importance of dwell time

As introduced, UVC light can kill COVID-19m which is why there are so many new businesses and patent applications popping up with purifying claims. However, many of these promises aren’t backed by the necessary rigour. In reality, UVC is just one aspect of an effective air purifier. A crucial factor is dwell time, which in other words, is how long the air is exposed to the UVC light.

For the coronavirus to be inactivated, it needs to be exposed to UVC radiation for 0.657 seconds. However, this dwell time is dependent on a number of factors. Primarily, there has to be a 440mm clear distance in the UVC chamber, where the emitters are located. If the distance is any less, this reduces the exposure time, thus lessening the effect of the radiation. 

Secondly, this calculation assumes the lamp is new; a UVC tube at the end of its life will need 1.095 seconds to fully purify the air. Equally, the lamp will need to emit at least 1056 microwatts, assuming the airspeed is 2 m/s. However, the wattage will need to be adjusted if the airspeed is higher or lower. As is evident, quality equipment and expert engineers are essential; fitting any old unit with UVC on the label is unlikely to achieve the desired results. 

Does the unit emit ozone? 

UV light disrupts the DNA/RNA of microorganisms – and that means it can disrupt our cellular structure too. Therefore, UV needs to be handled with extreme caution and units need to have the appropriate design to prevent exposure. However, there are other important safety features to take into account, perhaps most importantly, the production of ozone. 

Ozone is the molecule O3. Ozone is dangerous as when inhaled, it can cause lung damage. Even small quantities can cause chest pain, coughing, shortness of breath and irritation in the throat. It can be particularly harmful to those that suffer from chronic respiratory disease like asthma. It can also compromise the ability of the immune system to fight respiratory infections. 

A UV lamp ‘tuned’ to 185nm can create ozone from oxygen (O2) by disrupting the molecule and splitting it into two oxygen atoms, which in turn, attempt to attach to another oxygen molecule. This third oxygen atom creates ozone (O3). Therefore, it is essential that the unit is tuned outside of the ozone range. For example, Rejuvenair lamps are set at a frequency of 253.7nm, which kills germs without the risk of creating ozone.

Choose Rejuvenair for quality and safety

Rejuvenair UVC air purifiers are fitted with the only UVC lamps that are approved for medical and battlefield scenarios. Moreover, every unit is installed by our expert engineers who assess the area for variables that may impact the unit’s functioning. With their support and our quality, British-designed and built equipment, you can be confident your unit works – no compromises, not on quality, nor on safety.