About UV-C

UV-C is short-wavelength ultraviolet radiation. UV radiation is produced by the sun, and comes in three forms: UV-A, UV-B and UV-C.

 

UV-A and UV-B rays reach through the earth’s ozone layer, and we use UV protection (sunscreen) to protect our skin from these rays. UV-A is the least harmful form of ultraviolet radiation, while UV-B is the cause of severe sunburn and skin cancer. UV-C is more harmful than UV-B, however UV-C radiation is absorbed by the earth’s ozone layer so we are not generally exposed to it. We can manufacture bulbs, however, which produce strong doses of UV-C radiation. As UV-C is harmful to living organisms, it is produced for sterilising and decontaminating against viruses and bacteria. 

UV-C is proven to effectively kill bacteria and inactivate viruses remaining on surfaces or in the air after cleaning. It was first used in the 1930s to tackle the spread of tuberculosis and measles, though as those diseases became less prevalent, UV-C treatment became less commonplace. Today’s ultraviolet sanitisers are devices that can be used as and when you wish, giving you complete control over sanitising your premises for added peace of mind.

How Does Ultraviolet Sterilizing Work?

Direct exposure to UV-C radiation destroys the outer skin (the protein coating) of all viruses – including SARS-Cov-2, the strain that leads to Covid-19. This breakdown in the DNA structure renders the virus unable to reproduce or to be transmitted any further, effectively disabling it.

 

Using portable lamps to emit UV-C radiation over exposed surfaces in a room will inactivate any viruses, bacteria, fungi or mould found in those areas. UV-C lamps are often called “germicidal” because of their effectiveness in this respect.

 

Different viruses require different levels of exposure to be inactivated. For example, the coronavirus strain that causes the common cold (HCoV-OC43) would be disabled very quickly when exposed to UV-C, while SARS-Cov-2 (the virus that causes Covid-19) requires a longer exposure time to disable. Delivering a 99.9999% kill-rate of SARS-Cov2 can make all the difference. Many UV-C lamps currently sold for home usage are not so effective against SARS-Cov-2 (Covid-19) for this reason.

 

The portable Muv-X Ultraviolet Room Steriliser can deliver a 6-log (i.e. 99.9999%) kill dose of UV-C light over a 3m radius in just 15 minutes, effectively combating the SARS-Cov-2 (Covid-19) virus.

Why Use UV-C?

UV-C is an effective and reliable method of disinfection for any organisation. Some of the key benefits include:

  • Chemical-free: there are no lingering residues after use, so no impact on peoples’ health or on the environment
  • Combats viruses, bacteria, fungi and mould
  • Minimal disruption and downtime: you can enter the room immediately once the disinfection has been completed, so no need to wait or air out the room before it can be used again
Illustrates how UVC is an effective steriliser

Basic FAQs

Can using UV-C devices help prevent the spread of COVID-19?

Yes. If UV-C directly illuminates the virus at the effective dose level, then UV-C can play an effective role when combined with other disinfection methods.

As explained in the User Guide, users of UV-C devices must be protected to prevent UV exposure to the eyes and skin, and UV-C should never be used to disinfect the hands.

What is germicidal UV, and what is UVGI?

Germicidal UV (GUV) refers to using ultraviolet radiant energy to inactivate bacteria, mold spores, fungi or viruses. When the process is applied in a given location, it has generally been referred to as ultraviolet germicidal irradiation (UVGI).

Is all ultraviolet considered germicidal ultraviolet (GUV)?

No. Germicidal ultraviolet (GUV) – refers to short-wavelength ultraviolet “light” (radiant energy) that has been shown to kill bacteria and spores and to inactivate viruses. Wavelengths in the photo-biological ultraviolet spectral band known as the “UV-C,” from 200 to 280 nanometers (nm), have been shown to be the most effective for disinfection. UV-C wavelengths comprise photons (particles of light) that are the most energetic in the optical spectrum (comprising UV, visible, and infrared) and therefore are the most photo-chemically active.

Can other UV devices like UV-A insect traps also be used for GUV treatment?

No. UV-A and longer (visible) wavelengths do not have the same UV-C properties to kill bacteria and inactivate viruses. Their relative disinfection capability is minimal – perhaps a thousand times less effective than a low-pressure mercury germicidal lamp.

There have been only infrequent applications of wavelengths in the UV-A and violet range (e.g. 405nm), which require very high doses.

These methods are not practical in an occupied environment and not recommended for effective viral sterilisation.

The trace amount of UV-B emitted from some white-light fluorescent lamps probably has similar efficacy.

Light-emitting diodes (LEDs) have been available for some time in the UV-A region. The advantage of UV-A or visible-light LEDs is that they can easily be incorporated into LED-based luminaires, and there might be no need for users to wear protective gear.

However, the efficacy of violet or UV-A energy that is not also harmful to the skin or eyes is minimal.

lso harmful to the skin or eyes is minimal.

Does the ultraviolet in sunlight have a GUV effect?

Yes, particularly in the late spring and early summer when the sun is high in the sky and the UV index is high. At a UV Index of 10, the duration to achieve at least a three-log kill of bacteria (99.9% killed) is estimated as less than one hour.

Medical & Healthcare

General

The World Health Organization (WHO) official position is that the COVID virus is spread by contact with large respiratory droplets, directly or indirectly by touching contaminated surfaces and then touching the eyes, nose, or mouth. However, research is underway to determine the degree of airborne spread—meaning virus in particles so small that they remain suspended in the air.

Such aerosol results come from the evaporation of larger respiratory particles generated by coughs, sneezes, ordinary speech, singing, and possibly by faulty plumbing systems, as occurred with the severe acute respiratory syndrome (SARS) virus.

How much of the virus responsible for COVID-19 is spread by the airborne route is not clear. The recommendation for healthcare workers to use fitted respirators, rather than surgical masks, reveals an official concern for airborne transmission.

The possibility that inhaled virus may result in more-severe lung damage than acquisition by other routes—for example, via the mouth, nose, or eye—is currently being investigated.

How long do virus particles and bacteria remain airborne

This is important, but difficult to answer in a simple fashion and it depends on how the microbes were made airborne, e.g., from a sneeze or cough, or by being blown up from surfaces or dusted off clothes. The smallest particles (1- to 5-µm droplet nuclei) can remain airborne much longer than cough droplets—for many minutes or even hours.

How can airborne spread viruses be reduced?

Diagnosis of infectious cases and their isolation is a critical intervention, but transmission from asymptomatic persons plays an important role in community transmission. In the US, the Centers for Disease Control and Prevention (CDC) has recommended that everyone wear non-medical face covers to reduce spread by respiratory droplets, both large and small.

Healthcare workers are advised to wear well-fitted respirators designed to exclude airborne particles, in addition to following all contact precautions.

For the airborne component, ventilation, social distancing, and other means of air disinfection are expected to play a role. Natural ventilation outdoors and in homes can be highly effective where conditions are optimal for airflow and temperature.

Mechanical ventilation can be effective, but six to twelve air changes per hour (ACH) are recommended in general for effective air disinfection or dilution.

How does GUV work to disinfect air?

Commonly-used GUV lamps generate predominantly 254nm of UV radiant energy, close to the peak germicidal wavelengths of 265nm.

GUV radiant energy damages nucleic acids (DNA and RNA) by causing mutations that prevent replication, leading to the death of virtually all bacteria and the inactivation of all viruses – both DNA and RNA types.

Bacteria and viruses vary somewhat in UV susceptibility, with environmental organisms, fungal spores, and mycobacteria being relatively harder to kill than more rapidly replicating and non-environmental microbes and most bacteria.

But even fungi are effectively killed with high-dose UV, which is used to treat fungal contamination in air, for example.

Has GUV been useful in medical treatment facilities?

Yes. Some hospitals use portable GUV devices like the Muv-X to disinfect air and surfaces in unoccupied rooms as an additional measure to reduce the spread of healthcare-associated infections.

Medical treatment facilities are using GUV devices like the Muv-X in three primary ways:

1) upper-room GUV fixtures with air mixing, for controlling airborne pathogens in an occupied space;

2) mobile GUV units, to disinfect high-touch surfaces;

3) GUV in HVAC air handling units, to treat recirculated air and to reduce mould growth on cooling coils.

Mobile GUV units like the Muv-X were used in the People’s Republic of China in the initial response to COVID-19.

How do scientists measure methods for killing or inactivating harmful microorganisms and viruses?

The most fundamental concept in photobiology is the action spectrum (or relative response) for a given effect. This action spectrum extends from 235nm to 313nm and peaks at approximately 265nm. A wavelength of 254nm has a relative efficacy of 0.85; by contrast, 313nm in the UV-B range has a relative efficacy of only 0.01.

How useful are UV-C rays in disinfecting surfaces and PPE? Are UV-C Wands effective

UVGI (UV-C in the appropriate range) is an excellent surface disinfectant. The International Ultraviolet Association (IUVA) believes that UV disinfection technologies can play a role in a multiple barrier approach to reducing the transmission of the virus causing COVID-19, SARS-CoV-2, based on current disinfection data and empirical evidence.

UV-C helps to mitigate the risk of acquiring an infection in contact with the COVID-19 virus when applied correctly. This product will address the need to sterilise rooms to a higher standard. UV-C light has been used extensively for more than 40 years in disinfecting surfaces against a whole suite of human pathogens.

Source: Fluence UV Dose Required review IUVA: https://www.iuvanews.com/stories/pdf/archives/180301_UVSensitivityReview_full.pdf)

All bacteria and viruses tested to date (numbering many hundreds over the years, including other coronaviruses) respond to UV disinfection. Some organisms are more susceptible to UV-C disinfection than others, but all tested so far react at the appropriate doses.

COVID-19 infections can be caused by contact with contaminated surfaces and then touching facial areas (less common than person-to-person, but still an issue). Minimising this risk is key because COVID-19 virus can live on plastic and steel surfaces for many hours.

Standard cleaning and disinfection routines may leave behind some residual contamination, which UV-C can treat, suggesting that a multiple disinfectant approach is prudent.

It’s important to note that where the UV-C light cannot reach a particular pathogen, that pathogen will not be disinfected.

Reducing the total number of pathogens reduces the risk of transmission.

The total pathogenic load can be reduced substantially by applying UV to exposed surfaces, as a secondary process to deep cleaning. Many published studies conclude that UVGI lamps are effective in controlling the spread of infectious respiratory diseases. https://www.ajicjournal.org/article/S0196-6553(15)00757-9/fulltext

Can GUV be used to disinfect surgical masks and the N95 respirator mask?

Hydrogen peroxide (H202) vapour disinfection has been the most recommended method now in use. However, if this is not available, studies by several laboratories have shown surprisingly effective UV disinfection, even though UV photons will not have a straight-line pass through all the porous filter structure.

Therefore, forward-scattered photons have to penetrate the mask, and substantial doses are required. This should only be attempted within a light-tight enclosure. In the US, NIOSH and the FDA have issued temporary guidance on this important subject.

Are GUV wands effective for disinfecting surfaces?

Hand-held, compact GUV products have been marketed for more than a decade for disinfecting small objects such as cell phones.

Most of these emit less than 2mW/cm2 of 254nm UV-C at contact (ours is >12W/cm2 per bulb), meaning that the wand has to be held to the surface for several seconds to achieve effective multi-log unit disinfection.

Waving it over an object such as a postcard for one second will not provide reliable disinfection. These products typically employ a safety switch that senses when the emission is not directed downward (away from the eyes) and shuts off if turned upward. Even if safely used, these might provide a false impression of effective disinfection

GUV Safety

GUV Safety

UVGI lamp emissions can pose a workplace safety and health hazard to the eyes and skin if the lamps are improperly used or installed. However, these lamps can be used safely if workers are informed regarding the hazards and follow appropriate precautions. A great deal is known about the human exposure limits of 254-nm UV (UV-C) irradiation. Compared to the UV-A and UV-B in sunlight, UV-C is almost entirely absorbed by the outer dead layer (stratum corneum) and outer skin (outer epidermis), with very limited penetration to the deeper cellular layers of skin where new cells are constantly created. For comparison, the current daily safety limit of 254-nm UV-C for 8 hours is 6.0 mJ/cm2 whereas less than ten minutes of summer sun exposure at a UV Index of 10 can deliver the equivalent limiting daily safety because of its much more-penetrating UV-A and UV-B.
As it has no outer dead protective layer, the human eye is the organ most susceptible to sunlight and GUV. Exceeding the threshold level value (TLV) will result in painful irritation of the cornea similar to over-exposure on a sunny day, especially from sun reflected from water or snow. The damage is painful but transitory, with corneal shedding and replacement in a day or two.
There are no known long-term consequences from an accidental UV-C overexposure. Most eye injuries result from workers cleaning fixtures or working in the room without first turning off the fixtures.

Are there safety rules for GUV surface-disinfection lamps?

To ensure the safe use of UVGI lamps for surface disinfection, follow these guidelines:

• Cleaning staff should place temporary warning signs at access points to the area being disinfected. They should either vacate the area during disinfection or place opaque barriers between the UVGI lamp and room occupants. If these areas are required to be occupied during disinfection and exposures cannot be avoided, personal protective equipment (PPE) should be used.

• Low- or medium-pressure mercury lamps, UVGI LEDs or Far UV-C lamps: operators should wear plastic or glass face-shields to protect the eyes and face. Nitrile gloves or work gloves should also be worn to protect the hands and full-coverage clothing with tightly woven fabrics for all other exposed skin. • Pulsed xenon arc lamps: users should wear welding or cutting goggles to shield the eyes,

nitrile gloves or work gloves to protect the hands, and full-coverage clothing with tightly woven fabrics to cover all other exposed skin.

Do eye or skin hazards differ depending upon the lamp type used?

Low- and medium-pressure mercury UVGI lamps emit UV energy, which poses a hazard to the cornea and skin. Some UVGI LED devices emit near 270nm, which poses a risk to the cornea and skin. Far UV-C lamps which emit around 222nm can pose a danger to the cornea. However, recent studies have been inconsistent regarding the risk that Far UV-C lamps pose to exposed skin. This might be the result of varying glass envelopes, allowing some longer-wavelength radiant-energy transmission.

Pulsed xenon arc UVGI lamps emit UV and visible radiant energy that poses a hazard to the retina, cornea, and skin. Some pulsed xenon arc lamps are filtered so that only the UV energy for disinfection is emitted. Xenon arc lamps can also pose additional safety hazards if they are not maintained properly.

These GUV lamps are generally used only in industry, to sterilise food and pharmaceutical containers, but have also been used in GUV devices for hospital room disinfection. Maintenance and service should only be performed by authorised persons.

Will GUV increase my lifetime risk for skin cancer?

UV-C penetrates only the superficial layers of the skin and eye, with the shortest wavelengths hardly penetrating at all to living cells (epidermis), so only a very mild, transitory “sunburn” (erythema) occurs from accidental over-exposure of skin areas. Even though GUV lamps can pose a theoretical delayed hazard, incidental UV exposures in the workplace would not significantly increase one’s lifetime risk for cataract or skin cancer when compared to daily exposure to the UV radiant energy in sunlight. Solar UV is much more penetrating and reaches the germinative (new-cell producing) layers in the skin, with the result that skin cancer risk is significant, and sunburns can be severe. There is a small amount of UV-B (297, 303, 313nm) from a low-pressure mercury lamp, but this is insignificant unless exposures are experienced at least an order of magnitude or more above the safety limits for 254nm.

UV-C penetrates only the superficial layers of the skin and eye, with the shortest wavelengths hardly penetrating at all to living cells (epidermis), so only a very mild, transitory “sunburn” (erythema) occurs from accidental over-exposure of skin areas. Even though GUV lamps can pose a theoretical delayed hazard, incidental UV exposures in the workplace would not significantly increase one’s lifetime risk for cataract or skin cancer when compared to daily exposure to the UV radiant energy in sunlight. Solar UV is much more penetrating and reaches the germinative (new-cell producing) layers in the skin, with the result that skin cancer risk is significant, and sunburns can be severe. There is a small amount of UV-B (297, 303, 313 nm) from a low-pressure mercury lamp, but this is insignificant unless exposures are experienced at least an order of magnitude or more above the safety limits for 254 nm.

If the room has glass that permits vision into the room and a view of the UV fixtures, does that glass need to be shuttered or covered?

No. This is not necessary for safety reasons if the devices are standard 254nm UV-C lamps. Glass windows will block potentially hazardous UV-B and UV-C transmission, but should be covered if pulsed xenon lamps are in use.

Lamp Technologies

What types of lamp sources are used for GUV?

Lamp technologies include continuously emitting low- and medium-pressure mercury lamps, as well as pulsed xenon arc lamps. Studies have shown that these technologies—continuously emitting or pulsed—are comparably effective for disinfection. Pulsed sources may be more practical if rapid disinfection is required. Light emitting diodes (LEDs) and krypton-chlorine excimer lamps, which emit in narrow bands in the germicidal range (UV-C), are emerging technologies.

What is the most widely used lamp source of UV-C for GUV?

Hot-cathode germicidal lamps are identical in shape, electrical connection, operating power, and life to standard fluorescent lamps, with both linear and compact types available.

Maintaining the transmission of the lamp over its life is more difficult than for standard fluorescent lamps. Cold-cathode germicidal lamps are also available in various sizes, usually for shorter, smaller diameter lamps. Their operating characteristics are similar to those of hot-cathode lamps, but their starting mechanisms are different.

Approximately 45% of the input power from such a device is emitted at a mercury-discharge wavelength of 253.7nm, in the middle of the UV-C band. The second major emission line is at 184.9nm, but this emission is normally absorbed by the glass, since—if emitted through the glass, as it is with pure quartz—it would create ozone at levels far above the safety limit.

Are there higher-output UV-C lamps?

Medium pressure mercury (Hg) lamps are also used, particularly in water purification. Such lamps resemble high-pressure mercury lamps—they are much more compact—and use a clear or doped quartz envelope, depending on the application.

Other sources, such as the rare gas halogen (e.g. krypton-chlorine, Kr-Cl) discharge, have been shown to produce significant emission in the Far UV-C region (205 to 230nm). The advantage of sources such as those emitting 207nm or 222nm is that some bacteria and viruses’ deactivation rate appears to be relatively high. The effect of the emission on human skin and eyes is much reduced compared to the 253.7nm mercury emission.

However, depending on the glass envelope, small but significant levels of longer wavelengths may be of concern. At this time, such sources have been developed in the research laboratory, but their presence in the marketplace is still very limited in comparison to that of mercury lamps, and there is little experience yet with any widespread use.

Are there UV-C emitting LEDs available?

There are reports of companies developing LEDs that emit in the longer-wavelength UV-C region, generally at 265 to 270nm. Still, it’s likely to be a considerable time before commercially viable systems are brought to market

GUV Applications

How much UV exposure and time does it take to disinfect a room?

There are very sophisticated programmes to calculate the lamp sizes and in-air dose requirements in terms of energy required for space and radiant fluence (joules per square metre, J/m2) across a cross-section of a UV-C beam. But there is a much simpler evidence-based dose that has been developed over many years for TB control, typically specified as

about 17 mW of 254nm lamp-emission radiant power per cubic metre (m3) of space to disinfect the air.

Although this sounds too simplistic to be accurate, since the air in any room is always moving and mixing, one can correctly assume that all air will be treated—the better the air mixing, the sooner this will happen. Studies at the Harvard School of Public Health and elsewhere show log units of reduction equivalent to 24 ACH to achieve 80% reduction of transmission.

Of course, 100% reduction is not possible, because of the multiple modes of transmission. To disinfect surfaces, this depends on the type of surface and its cleanliness.

How can I check UV-C output to ensure effective disinfection?

There are a number of dedicated meters available; however, a wide range of scale is normally required, from 0.1 to 100 microwatts per square centimetre (µW·cm-2).

Safety readings require the lower range, and efficacy requires a range up to at least 10 mW·cm-2. A common practice is to have two calibrated meters: one in reserve and for reference. The two instruments should be periodically compared. The user should retain the manufacturer’s instructions, including a description of the meter, its safe use, and maintenance and calibration of it. Some healthcare facilities contract with a full, outside maintenance contractor that uses calibrated meters and correctly and safely replaces burned-out lamps. Some users retain a simple, less precise meter for staff to use, but the installer uses a professional meter.

How long would it take to treat a standard room?

Room sizes and layouts vary, but an average treatment time is approximately ten minutes.

The inspiration for this new product came from a request for help from a Thoracic and Transplant Consultant Surgeon in Dublin. Following her experience of using the Muv-X, she said: “They should be in every GP practice and hospital in Ireland”.

However, it’s important to point out that the Muv-X is not a “silver bullet solution” and does not remove the need for standard deep cleaning procedures.

The Muv-X markedly improves cleaning levels and provides an additional layer of protection for workers and room users. It adds greater security both before and after the deep clean process by removing virus and bacteria that might remain. The continuous and regular outbreaks of MRSA are proof of the limitations of standard deep cleaning.

This technology cannot see around corners or into shaded areas. It will not disinfect the inside pages of magazines which are not exposed. Depending on the room layout, it may need to be moved or repositioned several times to get the best possible result. Stacking units can help increase coverage

How does the Muv-X protect people against COVID-19 contamination in medical settings?

UV-C is well-proven in tackling MRSA and while COVID-19 is the ‘new kid on the block’, it is also well-proven against close relatives of COVID-19 in recent years. The International

Ultraviolet Association (IUVA) believes that UV disinfection technologies can play a role in a multiple barrier approach to reducing the transmission of the virus causing COVID-19, SARS-CoV-2, based on current disinfection data and empirical evidence.

UV is a known disinfectant for air, water and surfaces that can help to mitigate the risk of acquiring an infection in contact with the COVID-19 virus when applied correctly. This product will address the need to sterilise rooms.

UV-C light has been used extensively for more than 40 years in disinfecting drinking water, waste water, air, pharmaceutical products, and surfaces against a whole suite of human pathogens

(Fluence UV Dose Required review IUVA: https://www.iuvanews.com/stories/pdf/archives/180301_UVSensitivityReview_full.pdf).

All bacteria and viruses tested to date (many hundreds over the years, including other coronaviruses) respond to UV disinfection. Some organisms are more susceptible to UV-C disinfection than others, but all tested so far do react at the appropriate doses.

COVID-19 infections can be caused by contact with contaminated surfaces and then touching facial areas (less common than person-to-person, but still an issue). Minimising this risk is key because COVID-19 virus can live on plastic and steel surfaces for many hours.

Routine cleaning and disinfection may leave behind some residual contamination, which UV-C can treat, suggesting that a multiple disinfectant approach is prudent. Accepting “line of sight” issues which mean UV-C light cannot reach all parts of a room, some pathogens may remain.

However, in general, reducing the total number of pathogens reduces the risk of transmission. The total pathogenic load can be reduced substantially by applying UV to the many surfaces that are readily exposed, as a secondary barrier to cleaning.

Can GUV be used in the home?

Handheld, compact GUV products are sold but are considered a serious safety concern in a general household environment, where children, pets, or careless adults can easily be overexposed. These products are typically less than 10 watts, with open and exposed mercury lamps. They may come with a safety timer. A person would place the open lamp on a table or in a convenient location, set the timer for several minutes to an hour, and given a 10-second delay to exit the room and close the door quickly.

Will UV treatments affect plants, paint and other wall coverings?

Using UV rays will degrade paint, yellow plastics, and destroy air filters, depending on their composition. For example, UV-C irradiation of respirators to be reused should be a last resort in a pandemic.

Furthermore, shorter-wavelength UV photons have higher energy potential than longer-wavelength UV photons and may have an accelerated ageing effect on materials and paints.

UV-C may damage plants; therefore, hanging plants should not be placed in the disinfection zone in upper-room applications or in whole-room UV-C applications.

How effective are UV robots for surface disinfection?

Hospitals and healthcare facilities have rooms that can be closed off to individuals for a length of time. So-called “UV-C robots” have been used to move around a room to disinfect surfaces with UV-C in all directions. The UV-C radiant energy is normally emitted by long, vertical mercury lamps or pulsed xenon lamps. It is a challenge to estimate dosages, but very intense emission can cover much of the room in a relatively short time.

Further, by moving autonomously around the unoccupied workspace, it can expose surfaces that would not be easily reached by fixed GUV lamp installations. If good air movement is present, most air will be disinfected as well.

Surfaces with a thick buildup of residues may pre-absorb the UV-C photons before they reach the active virus or bacterium. As with all GUV systems, they should be considered an effective addition to standard infection control cleaning guidance. These mobile units should be used after terminal cleaning of patient rooms and bathrooms.

What potential role can it play in the equine sector?

This unit can be used to disinfect stables, which is particularly useful in the high-end racehorse sector. Room UV Sterilisers reduces the risk of infection and stops the spread of animal sickness. Healthy horses are a result of good hygiene and good disinfection practices. As many animal pathogens are airborne, UVC sterilisation can provide a clean living environment for your horses.

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