While proper cleaning and decontamination of fire apparatus and other equipment is not a new need, the COVID-19 pandemic has brought special attention to its importance. Fire and EMS agencies across the country are looking for effective and efficient ways to keep their crews safe.
Concerns of transmitting COVID-19 are also shared by public officials, business owners, and anyone responsible for maintaining public facilities, mass transit or gathering spaces. Several news stories recently have shone a spotlight on ultraviolet light as a possible way to kill the virus and disinfect surfaces and the air around us.
Ultraviolet light
Use of ultraviolet (UV) light to disinfect is not a recent discovery. It was first identified as a way to kill bacteria by Arthur Downes and Thomas P. Blunt in 1878. Since then, UV light has been used in disinfecting and sterilizing:
- Drinking water
- Wastewater
- Titanium implants
- Contact lenses
- Surgical suites
- Clean workrooms
- Food and food processing equipment
You may have also seen portable UV light machines used to thoroughly clean rooms in hospital emergency departments after they were used for a patient that was known or suspected to be infected with “superbugs” like MRSA or C. difficile.
Natural ultraviolet light comes from the sun in three forms:
- UV-A, 315-400 nanometers (NM) wavelength
- UV-B, 280-315 NM
- UV-C, 100-280 NM
UV-A and UV-B are the only forms that make it to the surface of the Earth, while UV-C is filtered out by the planet’s ozone layer. UV-A contributes to the aging of human skin and UV-B is responsible for sunburns and skin cancer. Ultraviolet A and B have minimal ability to kill bacteria and viruses without some form of catalyst to intensify and speed the reaction.
Ultraviolet C
UV-C, on the other hand, may be used as a disinfectant because it damages the DNA replication system of bacteria, viruses and fungi. As these agents need large numbers to harm their hosts, without effective replication, they are effectively dead in their tracks.
The downside is that UV-C is immediately harmful to our skin and eyes, even with exposure of only seconds. In light of the COVID-19 pandemic, the World Health Organization has specifically posted warnings that UV-C cannot be used to disinfect skin.
Facilities that use UV-C to clean rooms or equipment must use careful procedures and personal protective equipment to ensure that no one is exposed to the light. The area must be clear of anyone not wearing skin and eye protection. Many units have remote controls or delayed start timers to allow everyone to leave the area before the light is activated. Businesses that use UV-C lights often activate them overnight while the buildings are empty.
Far UV-C
Recently, scientists at Columbia University have been experimenting with a specific wavelength of UV-C light that may be effective in killing microbes while still safe for humans. Far UV-C refers to the narrow range of 207-222 NM, although much of the research is specifically on 222 NM UV-C.
While clinical testing is still underway, it does not appear that Far UV-C penetrates human skin to cause the damage that other wavelengths do. It still strong enough, though, to kill superbug bacteria and many viruses. Testing on COVID-19 has just started as high-security labs were needed to prevent the unintentional spread of the pathogen. Initial results are promising that it will be effective at disinfecting surfaces. The researchers are next testing whether it can kill the virus while it is suspended in the air.
Once thorough safety and effectiveness testing is complete, Far UV-C lights might be used to constantly disinfect surfaces, rooms, equipment, circulating air and even individuals that pass by.
Cleaning apparatus
In the meantime, existing UV-C technology is available for use in cleaning apparatus and other equipment with a few caveats.
The first is the limitation mentioned previously about the need to protect staff from the harmful UV-C light. Apparatus and equipment will need to be in a safe area where firefighters or the general public will not be exposed to the operating light source.
The next factor is the amount of time the unit needs to operate to be effective at killing bacteria and viruses. The exposure time is dependent on the bulb strength and manufacturer recommendations, but products currently on the market list 2 to 20 minutes.
Use of the UV-C light does not take the place of manually cleaning surfaces to remove any blood, dirt, or other organic material. Time must still be taken to wipe all surfaces with an approved cleaner.
The UV-C light coming from the unit will generally only disinfect areas that are in sight of the device. Any surfaces that are blocked from the light by other objects will not be cleaned. Some reflection of the light occurs but this greatly reduces its effectiveness. One study found that some surfaces took as long as 15 hours to receive enough light to be disinfected [2]. Due to the complex layout of most ambulances, the light will likely need to be moved to several different locations to eliminate shadowing and disinfect the entire patient compartment.
The effectiveness of a UV-C light may also be decreased if the bulb is dirty or damaged. Follow manufacture instructions for cleaning and maintenance.
How to buy UV-C systems for use in the fire service
If your department is considering purchasing a UV-C system to disinfect apparatus and other equipment, keep the following considerations in mind:
- Is it a medical-grade device? Especially with the recent pandemic, manufacturers are rushing to get products on the market. Make sure the unit you are considering is intended for medical use and has an appropriate strength light. The study cited below used a 60-watt bulb [2]. Units available for mounting in ambulances are listed at 35 watts.
- What is the expected lifespan of the bulb? Bulbs will generally last thousands of hours but they will eventually need replacement. What is the replacement cost? Also keep in mind that they contain mercury and will need proper disposal.
- What is the manufacturer’s recommendation for operating time? Will the unit need to be moved to different locations within the vehicle to be effective?
- How often will your units be disinfected with the UV-C device? Will it be on a regular schedule, after transports of suspected infectious patients or both? Will use of the device decrease unit availability and will it require additional staff hours to operate?
- How will you know if the device and process are effective? Test strips are available to check for the presence and strength of UV-C light. You may also partner with a lab to test surfaces for contamination after UV-C light treatment.
While they do not replace manual cleaning with approved disinfectants, ultraviolet-C light devices are worthwhile additions to the options fire departments have to clean apparatus and other equipment of the invisible bacteria and viruses we encounter when responding to calls.
References
1. Triomphe, C. (2020, May 10). Tests show UVC lamps could light the way in virus fight. Retrieved May 28, 2020, from https://medicalxpress.com/news/2020-05-uvc-lamps-virus.html
2. William G. Lindsley, Tia L. McClelland, Dylan T. Neu, Stephen B. Martin Jr., Kenneth R. Mead, Robert E. Thewlis & John D. Noti (2018) Ambulance disinfection using Ultraviolet Germicidal Irradiation (UVGI): Effects of fixture location and surface reflectivity, Journal of Occupational and Environmental Hygiene, 15:1, 1-12, DOI: 10.1080/15459624.2017.1376067
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