Staying Safe

Table of Contents

How you get infected

It has been understood since 2020 that Covid is airborne, the virus is aerosolised when someone infected breathes out. It is like smoke, it stays in the air for hours. Public health messaging, has, and continues to obfuscate this. Many people still believe that hand sanitising, surface disinfecting and maintaining social distance are useful measures.

Just to be clear – this messaging is deliberate, hand sanitising is about personal responsibility, you are responsible for your own safety. Air cleaning puts the responsibility and liability squarely on the owner of the space, ie businesses.

You get infected with Covid through being in shared air space. It is really easy to understand, just think about people smoking in a room.

The variables are the size of the space, air circulation, density of people and time spent. Illness is about viral load – which just means how much virus you inhale. Even if you can’t avoid being in a risky space, the less virus you inhale the better. Just because a room is empty when you enter doesn’t mean the virus is not still in the air from previous occupants. Outside transmission is rarer but not impossible, again just think about someone smoking.

You are not going to catch covid from shaking someone’s hand or giving them a hug, you are not going to catch it from touching a door handle (these things are not technically impossible but vanishingly unlikely).

Finally, risk is not binary. If you have to go to work in an office where no-one masks and there is no clean air mitigation, and you don’t feel like you can wear a mask there, it still makes sense to wear a mask on the train. Each situation is a separate chance to inhale virus, if you don’t mask on either you double your risk.

The only reason not to mask in a setting where you don’t know anyone, say a train or plane, is that you believe you are going to get infected from time to time anyway so it just isn’t worth constantly thinking about Covid because that makes life miserable, but this really stems from not properly understanding the risk. Again, if HIV was airborne and going to a pub meant you could get infected with HIV, you would not go to the pub. If it meant you would go home and infect your children with HIV you definitely would not go into the pub. So it is just that you don’t understand that Covid is airborne and acts on the body in a similar way to HIV.

Clean Air

This is not complicated – we get infected with Covid by breathing in polluted air, the solution is to clean the air we breathe.

Air cleaning is discussed in terms of equivalent air changes per hour, eg, an air purifier rated at 4ACH (for a room of x size) means using that filter is the same as if the air in the room was completely replaced with outside air 4 times each hour.

There are three main ways to clean air in indoor spaces;

  1. Ventilation – open windows whatever the weather
  2. Air filters – generally but not exclusively to a standard called HEPA
  3. UV light – this sterilises airborne pathogens on contact
  4. and for people working in healthcare – wearing a respirator so the virus doesn’t get exhaled into the air in the first place

Air quality can easily be measured using a CO2 monitor – note this is a proxy it doesn’t actually measure contaminants in the air – we breathe out CO2 so high CO2 indicates you are breathing in air that someone else has breathed out. The only problem is that using an air filter removes pathogens but not CO2, so the CO2 measure gives a false reading in this scenario, but given right now there is no air filtering anywhere CO2 is a really good way to see what the fresh air level is like.

To get some understanding of the impact air filters can make, a recent study from a school where some classes had filters and some didn’t, reported that over a long period, the parents of the children in the classes with the air filters had 30% less days off work with sickness. Take a minute to think how much sickness the children will have had on the way to that statistic.


Masks are engineered solutions, they are designed and tested to do specific jobs. You wouldn’t wear a surgical mask to handle asbestos. There isn’t anything else to add.

Far UV

Far UV is the thing that could take us back to a world where indoor spaces were properly safe again (short of a neutralising vaccine and governments that deploy public health measures). HEPA filters are known to reduce infection levels by reducing viral load in a room but make rooms safer – not safe. The same applies to ventilation. In both cases very close contact can infect faster than the air gets changed.

UV light kills viruses almost immediately and has been used for nearly a hundred years controlling infectious disease outbreaks. Ultraviolet light from the sun covers a range of wavelengths (UVA is 315-400nm, UVB is 280-315nm) and as we know is harmful to human skin. As the wavelength reduces the UV light’s ability to penetrate the deeper layers of human skin is reduced, by the time we get down to 222nm the light in unable to penetrate the very top layer of the skin, this is what is referred to as Far UV.

The Far UV lights in use today emit UV light that is almost entirely at or very close to 222nm but there is a distribution curve and small amounts of higher frequencies do get emitted. Some manufacturers employ filters to eliminate even more of the out of range wavelength light but these reduce the 222 light at the same time.

The intensity of the UV light reduces exponentially as distance from the source increases so device power has to be as high as can safely be supported and most devices include LIDAR to turn the power off if someone is detected too close to the device.

Many of the devices available utilise the same UV lamp module, which is the Ushio Care 222. This doesn’t mean all the devices are the same though as different devices use different diffusers (to give a wider area of coverage but which absorb power) and even bespoke power units.

There are two very different types of application, fixed devices to cover rooms and personal devices for use at work desks, on transport, in restaurants or for example at the dentist (where the dentist has not installed room level protection!)

The personal devices are lower power to make them safe for use within close proximity but there are valid concerns as to whether this makes them ineffective. As of early 2024 a good example of a personal device is Far UV Technologies’ MVP device although this is a constantly changing world so always research if thinking of investing. This device disinfects a 2 foot to 3 foot dome in around 4 minutes, so in terms of the restaurant scenario this seems a bit pointless as the air is constantly moving. The manufacturer says the following – “Approximately 18” from the unit will generate a 40% reduction in most mammalian viruses in 30 seconds”. We are not in a perfect world so you could interpret this as saying it doesn’t make enough air safe to be worth the investment, the MVP is currently US$499, or you could interpret it as saying that it makes a meaningful impact in reducing the viral load. We know the likelihood of developing a serious PCC is linked to the amount of virus you are exposed to so there is a strong argument that just because these devices are not perfect does not mean they are not a very useful additional tool.

A good way of thinking about anything like this is to say – if it was free, would you do it? Clearly yes, it makes a meaningful impact. So really the question is, does the cost make sense? This is obviously a personal judgement.

The problem for most people at the moment is that Far UV solutions are quite expensive. The personal device mentioned above is $499. Small room level devices are around $1,200 to $2,500 but don’t last forever so you need to factor lifetime into the buying equation and devices for bigger areas get more expensive!!

At the small room level, so resturants, healthcare consultation rooms, school classrooms, there is a wide range of devices and device types, from devices that are mounted on stands, to those designed to be wall mounted to ceiling downlights and pendants. The manufacturers are generally very happy to engage in discussions to help identify the right solution.

Far UV is cheap compared to other solutions that could make air equally safe – but that does not mean they are not a lot of money for most people and businesses to invest in compared to deciding to do nothing. In the case of most businesses this is a hard decision because lack of covid precautions is not going to impact business at the moment, but at some point we have to assume sanity will prevail and clean indoor air will become a basic requirement.

As with all things covid, the dark money libertarian groups are trying to discredit Far UV, so there are stories about Far UV devices creating ozone which is in itself dangerous. Unsurprisingly this does not stand up to any scientific analysis as the claims do not have any facts behind them, there are very strict standards in place and the devices available create tiny amounts of ozone compared to any safe standard.. Eyes are more sensitive than skin so arranging the device to avoid staring into it is sensible, light from above is less risky so ceiling installations make sense where possible.

This video is a webinar delivered by the CEO of Far UV Technologies. It is very long, just over an hour to the end of the main presentation as he is clearly an expert on Far UV but not on delivering webinars…. a large section at the start is background but it is all interesting and the main body gives you a really good understanding of all aspects of Far UV. Worth saying the webinar is promoting their business and products but it is nevertheless the best detailed explainer I have come across and will give you a good grounding in all the issues surrounding this technology. Link to webinar video

A detailed study, published in Nature, shows the effectiveness of Far UV and provides good background on the science and state of knowledge.


If cost is no issue you would definitely install Far UV, where HEPA can achieve 5-6 equivalent air changes per hour, Far UV is at 30++

It is difficult to assess the level of virus elimination a particular device will give in a real world setting, but it is an engineering solution, Far UV definitely kills airborne pathogens, a Far UV device will definitely reduce the risk even though it may not eliminate it.

The devices are too expensive to expect mainstream adoption in the short term

The value of reduced staff sickness would easily justify the investment but first we need acceptance that the unprecedented levels of sickness are linked to constant covid reinfection.

Not being responsible for an entire generation of sick kids would also merit consideration, you know, you would think

The following product sites are worth looking at as a starting point;

Far UV Technologies

Moore Medtech

My Lumens

Important note – this page is only intended to help people gain a basic understanding of the issues around Far UV, it is written for people who have formed their own view that they want to consider investing in the technology. I am not an expert, I have just done research and spoken to a couple of manufacturers. This is passed on here to help others get started, anyone investing in Far UV needs to do their own research, I have not seen any real world trial data although I believe case studies exist, I am not recommending any product and not making any claims about the effectiveness of the technology in real word settings.