Understanding air filtration and UV disinfection in a medical environment

Health Europa reports on why UV purification is the most effective air disinfection method for medical, commercial and residential environments.

Evidence has accumulated over the years that following the standard guidelines and codes for designing healthcare facility ventilation systems is far from sufficient to ensure a sterile environment. Sterility is generally defined as 6 log (99.9999%) reduction of a population of microorganisms. This means that as little as one microorganism in a million is expected to survive after disinfection.

Traditional air filtration with high-efficiency particulate air (HEPA) filters or ultra-low penetration air (ULPA) filters have been widely adopted in the ventilation systems of hospitals, labs, and clinics, to control airborne pathogens. However, multiple studies have demonstrated that despite the use of such high-end filters, viral and bacterial airborne contamination are still ubiquitous in these ventilation systems. 

The most common explanation for underperforming filters often points to the filter rack seal joint’s bypass, filter puncture leakage, and poor general installation or maintenance. Although all these points remain valid and can always be improved, the physical cause is rooted in the fundamental fact that all filters show a significant drop in their capture efficiency for a certain range of particulate sizes – these can include both particles which are too small to be captured by interception and impaction and those which are too large to be removed via electrostatic and diffusion. This is simply a straightforward consequence of the fundamental principles of filtration physics. […]

Read more on Health Europe website.

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Using Sanuvox UVC technology to reduce the propagation of SARS-CoV-2 virus

Using Sanuvox UVC technology to reduce the propagation of SARS-CoV-2 virus

  • UVC irradiation (254 nm) is known for its germicidal properties. By disrupting their nucleic acids (DNA/RNA), it inactivates the reproductive capability of biological pathogens (molds, viruses, bacteria).1, 2

  • Sanuvox in-duct units have been demonstrated to be up to 99,97% effective at inactivating viruses and bacteria in the air in a study conducted by the EPA and Homeland Security 3. Bacteria and virus tested in the study (B.atrophaeus, S.marescens, MS2) are known to be more resistant to UVC than SARS-CoV-2 virus. 4,5
  • Many engineering and health agencies (ASHRAE, REHVA, CDC) now recognize that airborne transmission plays a major role in the propagation of SARS-CoV-2, the virus responsible for COVID-19. These agencies also recommend using UVGI as an effective method to mitigate the spread of the virus in indoor spaces. 6, 7, 8, 9
  • Because Sanuvox units are specified according to HVAC systems parameters, adequate UV output power is calculated using our proprietary software. As such, patented Biowall units can achieve the recommended 99% disinfection per pass regardless of air velocity.
 

1 https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/uv-lights-and-lamps-ultraviolet-c-radiation-disinfection-and-coronavirus

2 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789813/

3 https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NHSRC&address=nhsrc/&dirEntryId=154947

https://www.springer.com/gp/book/9783642019982

5 https://www.researchgate.net/publication/339887436_2020_COVID-19_Coronavirus_Ultraviolet_Susceptibility

https://www.ashrae.org/about/news/2021/ashrae-epidemic-task-force-releases-updated-airborne-transmission-guidance

7 https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/scientific-brief-sars-cov-2.html

https://www.rehva.eu/fileadmin/user_upload/REHVA_COVID-19_guidance_document_V4_09122020.pdf

9 https://www.ashrae.org/technical-resources/filtration-disinfection

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El Periódico reports on a new method of disinfection (article in Spanish)

El Periódico reports on a new method of disinfection (article in Spanish)

Utilizando la combinación de la luz UV, la nebulización o microdifusión molecular, la pulverización y la aplicación directa para la eliminación del SARS-Cov-2.

ASEPT2X_Modible_UV_Sterilizer-app-05-resized

Equipos UV EULEN Limpieza Hospitalaria. / EPDA

EULEN Limpieza, actividad del Grupo EULEN, líder en nuestro país en el diseño de servicios a empresas y siguiendo con su objetivo de ofrecer a la sociedad servicios innovadores que aportan soluciones útiles, de calidad y sostenibles, ha concluido -tras multitud de ensayos realizados por su departamento Técnico de higienistas exclusivo para el entorno Hospitalario y de un equipo de I+D+I- que la mejor técnica para eliminar virus, bacterias, hongos y agentes contaminantes orgánicos similares en entornos sanitarios es una combinación de diferentes técnicas aisladas.

La efectividad que cada una de ellas tiene en diferentes aspectos, hace que dicha combinación de técnicas específicas como laluz UV, la nebulización o microdifusión molecular, la pulverización y la aplicación directa sea la técnica definitiva en la limpieza hospitalaria frente al SARS-Cov-2.

Tecnología puntera

Actualmente la compañía dispone de los equipos más avanzados a nivel mundial y que otorgan una máxima seguridad de utilización tanto para los operarios que los manejan como para cualquier usuario del espacio tratado, especialmente en el ámbito hospitalario.

Destacan las unidades del equipo Asept.2x de Sanuvox Technologies, empresa canadiense líder de su sector. Este dispositivo puntero en desinfección por luz ultravioleta se utiliza tanto en quirófanos como en habitaciones. La luz UVC y la luz UVV del equipo tienen la misma longitud de onda que la producida por el Sol y ataca a los microorganismos a nivel molecular, desactivando y destruyendo los contaminantes, así como degradando los agentes químicos y olores. A diferencia de las lámparas convencionales, los sistemas de purificación UV que utiliza EULEN Limpieza usan un proceso patentado diseñado para entregar la máxima cantidad de luz UV.

Para complementar el sistema de desinfección por UV, la compañía emplea la última tecnología en nebulización y pulverización de generación de niebla nano y micrométricacon dinámica inductiva. Es la misma tecnología que en la actualidad está siendo usado también por las Unidades Tecnológicas de Cuerpos de Seguridad del Estado en la lucha contra el Sars-COV-2. Dotado con la última tecnología de desinfección mediante chorro regulable que permite desinfectar las estancias en un corto tiempo, minimiza tanto el desinfectante utilizado como los residuos y posibles daños a personas e infraestructuras. Asimismo, permite tratar grandes áreas en cortos periodos de tiempo, accediendo a todas las superficies y zonas de difícil acceso, realizando el perfecto mojado de todas las superficies a desinfectar.

Por último, de acuerdo a su política de utilización de los mejores biocidas del mercado, desarrollados por las empresas líderes, junto a los profesionales formados y acreditados acorde con la normativa establecida por el Ministerio de Sanidad en cuanto a la aplicación de Biocidas,se selecciona en cada momento el más conveniente para aplicar por el método óptimo en función de las necesidades. Por ello, es importante distinguir entre los de un espectro más específico de los de amplio espectro.

En definitiva, la combinación de todas estas técnicas y tecnología se convierten en la mejor solución frente a la COVID-19 en espacios hospitalarios y aseguran un resultado óptimo en desinfección en el menor tiempo posible.

En la actualidad, numerosos hospitales de la Generalitat Valenciana y otros de referencia en la geografía española confían en las soluciones de EULEN Limpieza cuya estructura y forma de trabajo propia asegura el mejor resultado en un entorno como el sanitario.

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El Mundo reports on ASEPT.2X in Spain (article in Spanish)

El Mundo reports on ASEPT.2X in Spain (article in Spanish)

Para Héctor Atienza

La Clínica Universidad de Navarra emplea un máquina pionera en España que desinfecta de COVID-19 las habitaciones del hospital en poco más de cinco minutos con rayos UV. Estos modelos se fabrican en Canadá y cada equipo cuesta hasta 160.000 euros.

Dos máquinas UVR desinfectando un quirófano en la Clínica Universidad de Navarra.

La lucha contra el Covid-19 también se pelea estos días al milímetro en cada rincón de los centros hospitalarios por los equipos de limpieza. El coronavirus ha demostrado tener una alta capacidad de transmisión y fácil apego a todo tipo de materiales de forma invisible. Su resistencia complica las labores de desinfección de las salas en plena crisis sanitaria.

Una de las técnicas más innovadoras en esta particular batalla contra el virus son las lámparas germicidas de irradiación ultravioleta (UVGI). Con esta tecnología tanto las estancias de los hospitales como los quirófanos quedan libres del bicho tras su paso en un corto periodo de tiempo.

“Son muy efectivas porque destruyen tanto el ADN como el ARN, donde está la programación genética de los virus y las bacterias. Una destrucción total en poco tiempo que permite el acceso casi inmediato a las estancias”, destaca el doctor de la Clínica Universidad de Navarra, Francisco Guillén Grima, cuyos centros en Madrid y Pamplona aplican esta técnica pionera de trabajo.

Se trata de una tecnología relativamente novedosa en España. Con las técnicas tradicionales de esterilización de espacios, como el peróxedo de hidrógeno y las botellas de gas o vapor, los pacientes deben esperar entre una y tres horas para poder acceder a la habitación. Mientras que los equipos ASEPT-2x UV permiten su entrada en poco más de 10 minutos después de la salida del último paciente.

El médico Guillén Grima posando junto a un modelo ASEPT-2X UV.

“Las recibimos hace justo ahora dos años. La primera vez que las utilizamos fue porque se había intervenido quirúrjicamente a un paciente infeccioso, pero el quirófano se necesitaba urgente para un transplante cardiaco. En estos casos, te avisan cuando hay una posible donación y se debe actuar de inmediato. Metimos las dos torres y en 20 minutos el quirófano estaba operativo“, añade Guillén Grima que también fue uno de los 70 científicos que firmaron el manifiesto enviado en marzo a Pedro Sánchez solcitando el confinamiento de la población.

Fabricados por la firma canandiense Sanuvox, los equipos tienen una altura de 1,60 metros y poco más de 71 centímetros de ancho. Con apenas 45 kilos de peso, su transporte se realiza de forma sencilla con sus ruedas guía por todas las dependencias del hospital.

El único inconveniente que pueden tener estos equipos son las zonas de sombra que genera la lámpara UV cuando actúa. Para contrarrestar este hándicap, el personal técnico sitúa la máquina en varios puntos de las habitaciones evitando así cualquier recoveco con virus.

“Uno de los equipos se compone de dos torres que trabajan simultáneamente y cada lámpara se activa cinco minutos. Pero ahora con el tema de coronavirus hemos subido a seis minutos para asegurar la desinfección como un margen de seguridad total. Con la crisis del coronavirus también hemos alquilado cuatro torres más porque no dábamos a basto“, añade el especialista.

Son equipos caros. Según ha podido confirmar EL MUNDO, cuestan entre 60.000 y 140.000 euros, en función de las características del modelo. Algunos fabricantes ya ofrecen versiones que se mueven de forma autónoma por las instalaciones hospitalarias. Sin embargo, la clave del equipo está en el software que registra la máquina vía Wifi en el servidor del hospital. Pueden ofrecer diferentes soluciones tanto de servicios como de control de salud.

“Al quemar el polvo, también se produce cierto olor que se va enseguida. Si quieres que no huela a ozono, hay modelos que llevan unos filtros, pero la máquina cuesta más cara”, destaca el doctor Guillén Grima.

Estos equipos, que en España son distribuidos por la empresa tecnológica Alfatec Sistemas, también están presentes en los centros de la Fundación Jiménez Díaz en Madrid, del grupo QuirónSalud, y en la empresa de servicios generales Eulen.

LÁMPARA PARA UTENSILLOS

La técnica de desinfección ultravioleta, con una lámpara de pequeñas dimensiones, también se utiliza en los hospitales para limpiar de gérmenes en equipos de uso habitual entre pacientes y en parte del material médico. Sin embargo, este equipo también hace una especial labor desesterilizando los mandos a distancia de las televisiones.

“Es un equipo que se toca mucho por pacientes y acompañantes. Nosotros ahora los metemos en la máquina y salen dentro de una bolsa precintada. También los usamos con los termómetros, endoscopios… Es una técnica nueva que tendrá mucho futuro en España”, añade el médico.

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Sanuvox UV air purifiers capabilities against viruses

Sanuvox UV air purifiers capabilities against viruses

Sanuvox corporation, a North American leader in UV disinfection of air and surfaces, would like to warn people tempted to purchase air purifiers or other devices against potential claims that would find themselves misleading.

UV air purifiers installed in the HVAC system, with an adequate germicidal dosage sized for the air flow, will destroy airborne viruses, but cannot guarantee anyone from becoming infected.

Air purifiers inside HVAC cannot disinfect frequently touched surfaces such as door handles and light switches, which are common disease transmission path. So good hygiene practice and frequent wash of hands continue to be the safest way to protect ourselves against any airborne or surface contaminants that can be introduced by other occupants and dispersed by the HVAC system in the house.

In other words, a powerful UVC air purifier can reduce the possibility of spreading the contaminants through the HVAC system, but it does not eliminate the necessity of safe hygiene practices.

 
Because the susceptibility to germicidal UV of any microorganism is determined by its genome sequence, the germicidal UV dose required to kill the CoVid-19 is practically the same as for the SARS-CoV (2003) within less than 1.6% variance.
 

For additional technical information regarding Covid-19, please visit https://bit.ly/38t12Mo.

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Collingwood Hospital first in Canada to have self-sanitizing Patient Rooms

BradfordToday reports on Collingwood hospital first in Canada to have self-sanitizing patient rooms

By Erika Engel

UV light, ozonated water, copper-infused surfaces, and titanium dioxide have all come together to make Canada’s first self-sanitizing patient room and bathroom at Collingwood General and Marine Hospital.

There’s copper in them there walls.

Collingwood General and Marine Hospital (CGMH) has opened the first of five self-sanitizing rooms, and will be the first hospital in Canada to use copper-infused panels on the walls in its hallways and patient rooms to prevent bacteria growth. 

Copper is naturally anti-bacterial and copper surfaces prevent bacteria growth.

The made-over patient room is located on the medical floor, and it’s packed with the latest technology in sanitization from the UV lights on the ceiling to the copper-infused toilet seat in the bathroom.

Norah Holder, CGMH president and CEO, said Collingwood’s hospital is the first in Canada to combine all of the self-sanitizing elements into one patient room and bathroom.

The bacteria-fighting technology includes copper-infused high touch surfaces like the bed rail, the door handles and pulls, the toilet seat, and the toilet handle. There’s UV lights on the ceiling that run on a disinfecting cycle when the patient is in the bathroom or outside the room, and there are plastic panels on the bottom half of the wall coated in titanium dioxide, which reacts with UV light to kill bacteria. In the bathroom a no-touch sink is engineered to prevent splashing and delivers ozonated water. Ozone has been proven to have an oxidizing, antiseptic, and germicidal effect. More UV lights in the bathroom activate after every use, bathing the room in UV light, which destroys the cell wall of bacteria, spores, and fungus.

The next rooms completed will have copper-infused panels covering the bottom half of the walls.

According to John Widdis, manager of operations and maintenance at CGMH, Collingwood will be the first hospital to use these panels as they are new to the market.

He said the technology doesn’t take away the need for cleaning, rather it mitigates the bacteria load on surfaces in the room. Rooms will still be cleaned once every 24-hours at minimum.

Swab tests showed bacteria counts in the range of 7,000 to 8,000 in a typical room. After the self-sanitizing technology was installed, the same swab tests are showing bacteria counts in the range of 30-50.

Dr. Michael Lisi, chief of staff at CGMH, said he’s “thrilled” to see CGMH become a leader in infection control technology locally, provincially, and nationally.

“This technology is really going to provide benefits in terms of patient safety, and safety of staff and visitors,” said Lisi. “I can have faith in such technology to provide the best level of care for our patients. This will help with improving outcomes and getting patients back to their families safely.”

CGMH has been testing some of the technology in its emergency department already. Widdis said he wanted to start with the one public washroom in the department once he watched the constant flow of people using the facility. The bathroom was cleaned once every 1.5 hours, but in between there would be eight or so people using it.

When the emergency department was renovated in 2016, Widdis had an ozone sink and some other self-sanitizing technology installed in the bathroom. Staff sinks were also replaced with models that delivered ozone water.

Since then, the hospital has seen the lowest rates of C-Difficile occurrences in recent history.

Lisi said the rates are the lowest they’ve been in six years. Widdis said the rates went down almost as soon as the changes were made in the emergency department.

“[Infection control] is a very significant component,” said Lisi. “It’s something all hospitals struggle with … C-Difficile can be life ending in elderly and those whose immune systems are not strong enough.”

Widdis has been at CGMH for 29 years and he’s seen hospitals and researchers work to battle hospital acquired infection rates over the course of his career.

In the beginning, said Widdis, it was done with chemicals, later it was bleach and hydrogen peroxide on surfaces. Before the UV lights, copper infused materials, and ozone water sinks, the last innovation was a “bomb” that would vaporize hydrogen peroxide to sanitize surfaces.

“We still use some of them,” said Widdis, adding the chemicals have moved to more earth-friendly compounds. “These are just more weapons we use in our fight against hospital acquired infections.”

The technology now installed on the medical floor will also continue to work against mutating strains of bacteria.

Widdis said staff decided to start installing the technology on the medical floor because it’s where patients would be isolated in cases of infection.

“If we have an outbreak, which we haven’t in years, this is the floor where we run into the most trouble,” said Widdis.

Work is continuing to outfit four more patient rooms and renovate hallways to include fresh paint and copper-infused panels on the walls. There are also plans in the works to outfit all hospital bathrooms with copper-infused toilet seats, high touch areas, ozone sinks and UV light.

For rooms not equipped with UV lights yet, the hospital has two portable towers with UV lights that can be used to disinfect any room.

Holder is looking forward to using this and even newer self-sanitizing technology in the future hospital build.

The CGMH foundation raised $1 million for the project through the Tree of Life campaign held at Christmas and other initiatives.

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Root Cause of the Odor Generated by Germicidal UV Disinfection with Mobile Units

Root Cause of the Odor Generated by Germicidal UV Disinfection with Mobile Units

By Normand Brais, P.Eng., M.A.Sc., Ph.D. and Benoit Despatis, Eng. ASHRAE Member

INTRODUCTION

It has been often noticed by many users over the years that whenever a germicidal UV surface disinfection is performed in a room, there is almost always a strange odor left afterward. It is not the smell of ozone, which can be easily identified and measured. It is more like a slightly pungent smell similar to rotten eggs or burnt hair. It is actually easier to recognize the smell than to describe it. Up to now, no satisfactory explanation as to the origin of this peculiar odor has been provided.  Several working hypothesis have been explored to explain this awkward phenomena:

1) Off-gassing of wall surfaces such as paint or other volatile materials.

2) UV lamps end caps glue off-gassing.

3) UV lamps connectors or end rubber boots overheating.

4) Interaction of UV with airborne and surface-borne dust.

After several tests and experiments, the first three hypotheses were quickly ruled out as a potential root cause. Off-gassing of paint was eliminated after testing in a bare metal aluminum enclosure and witnessing the same odor.

The UV lamps end caps were completely removed and all the glue removed with no effect. The same was done for the lamps connectors and also showed no impact on the odor. However, while we were performing these tests, it was noticed that when the disinfection cycles were repeated several times in the same enclosure, the perceived odor level after each cycle seemed to be diminishing. This was the hint that leads us to focus our attention on the presence of dust particles in the air, what these particles consist of, and how UV can potentially alter them into perceptible odorous compounds.

COMPOSITION OF AIRBORNE DUST

Airborne dust in homes, offices, and other human environments typically contains up to 80% of dead human skin and squamous hair, the rest consists of small amounts of pollen, textile fibers, paper fibers, minerals from outdoor soil, and many other micron size materials which may be found in the local environment1,2. In a typical indoor environment, the airborne dust volumetric load is somewhere between 100 and 10,000 μg/m3 (0.000044 to 0.0044 grain/ft3) order of magnitude. The dust load depends upon the occupancy rate, type of human activity, air filtration system efficiency, etc. It is worth noting that the maximum acceptable ASHRAE level for total dust is 10,000 μg/m3 (0.0044 grain/ft3) and 3,000 μg/m3 (0.0013 grain/ft3) for PM10.

Since airborne dust is essentially dead human skin and squamous hair pieces, it is worth taking a closer look at the fundamental material they are made of. The main constituent of human skin is a molecular group called keratin. Keratin is a family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble. Keratins encloses large amounts of the sulfur-containing amino acid cysteine, required for the disulfide bridges that confer additional strength and rigidity by permanent, thermally stable crosslinking; a role sulfur bridges also play in vulcanized rubber. Human hair is approximately 14% cysteine. Cysteine3 is an amino acid with the chemical formula HO2CCH(NH2)CH2SH. The pungent smell of burning hair and rubber is due to the sulfur by-products. The average composition of human hair consists of 45.2 % carbon, 27.9% oxygen, 6.6% hydrogen, 15.1% nitrogen and 5.2% sulphur.4

INTERACTION OF UVC WITH KERATIN AND CYSTEINE

When high energy UV-C light photons hit a keratin/cysteine molecule, they have enough power to break their internal chemical bonds and shatter them into many smaller molecules. The energy of germicidal UV photons at 254 nm wavelength is 470 kJ/mole, a value greater than the energy of chemical bonds listed in Table 1. It is therefore quite clear that proteomic molecules such as keratin and cysteine can be broken up by germicidal UV irradiation but not by visible light, for which the average wavelength is 550 nm, and the maximum photon energy only 217 kJ/mol.

 

Table 1. Chemical Bonds Strength5

Chemical Bond

Chemical Bond Average Energy
(kJ/mol)

C – C

347

C – H

413

C – N

305

C – O

358

C – S

259

N – H

391

Therefore, some of the chemical bonds between carbon atoms and hydrogen, nitrogen, oxygen and sulfur atoms will be broken by germicidal ultraviolet photons. Some of the resulting broken pieces of molecules following a sufficiently intense UV photon bombardment will contain sulfur and therefore fall into a category known as thiol molecules. Thiols are a family of sulfur compounds also called mercaptans. Their smell threshold is extremely low. The human nose can detect thiols at concentrations as low as 1 part per billion. The rotten egg-garlic smell is a dominant characteristic of mercaptans as shown in Table 2.

Burning skin emits a similar smell as thiols, while setting hair on fire produces a sulfurous odor. This is because the keratin in our hair contains large amounts of cysteine, a sulfur-containing amino acid. The smell of burnt hair can cling to nostrils for days.

 

Table 2. Reported Sensory Threshold for Thiol / Sulfur Compounds6

Compound Name

Chemical Formula

Sensory Description

Smell Threshold (ppb)

Hydrogen Sulfide

H2S

Rotten egg, sewage-like

0.5 – 1.5

Ethyl Mercaptan

CH3CH2SH

Burnt match, sulfidic, earthy

1.1 – 1.8

Methyl Mercaptan

CH3SH

Rotten cabbage, burnt rubber

1.5

Diethyl Sulfide

CH3CH2SCH2CH3

Rubbery

0.9 – 1.3

Dimethyl Sulfide

CH3SCH3

Canned corn, cooked cabbage, asparagus

17 – 25

Diethyl Disulfide

CH3CH2SSCH2CH3

Garlic, burnt rubber

3.6 – 4.3

Dimethyl Disulfide

CH3SSCH3

Vegetal, cabbage, onion-like at high levels

9.8 – 10.2

Carbon Disulfide

CS2

Sweet, ethereal, slightly green, sulfidic

5

CALCULATION OF RESULTING SULFUR COMPOUNDS CONCENTRATION IN AIR

In order to confirm the hypothesis linking the origin of the post-UV disinfection smell to the presence of keratin and cysteine in the air dust, a straightforward molecular concentration calculation was performed.

Given the dust loading, and assuming that this dust consists of 80% skin or hair, both of these containing around 5% sulfur that will end up being broken down by UV into the smallest thiol molecules such as Methyl Mercaptan, Ethyl Mercaptan or even Hydrogen Sulfide, the concentration of Thiol can be estimated as follows:

Where:

Dustload = dust weight per unit air volume in μg/m3 (lb/ft3)

SK = % Sulfur in Keratin/Cysteine = 5%

%Skin_Hair = Skin and Hair mass fraction in the dust = 80%

ρThiol = Methyl Mercaptan density at normal ambient temperature and pressure = 1.974 kg/m3 (0.1232 lb/ft3)

Equation (1) shows that when the airborne dust load gets above 75 μg/m3 (0.000033 grain/ft3), which is frequently the case in occupied spaces, the level of thiol generated by the shattering of keratin proteins exceeds the smell threshold of 0.5 to 1.5 ppb. It follows that even in the case of a relatively clean environment with dust loading as low as 100 μg/m3 (0.000044 grain/ft3), the aftermath of the UV disinfection process will leave behind a concentration of 2 parts per billion, which is greater than the smell threshold level, thus leaving behind a perceptible smell. Plotting a graph of equation 1 and allowing the dust loading to go up to 1,000 μg/m3(0.00044 grain/ft3) shows that unless the dust does not contain much dead skin or hair squames, the UV disinfection of a room will almost always leave behind a thiol concentration that exceeds the smell threshold.

Figure 1. Thiol Concentration in ppb vs. Dust Load

At maximum ASHRAE acceptable airborne dust loads of 10,000 μg/m3 (0.0044 grain/ft3), concentration of thiol could end up being as high as 200 ppb after UV disinfection. According to the US National Institute for Occupational Safety and Health7 (NIOSH), the IDLH (Immediate Danger to Life or Health) level for Methyl Mercaptan is 150 ppm i.e. 150,000 ppb. Also, according to CSST in Quebec as well as OSHA8 (Occupational Safety and Health Administration), the acceptable TLV-TWA (Threshold Limit Value-Time Weighted Average) level for 8hr exposure is 0.5 ppm i.e. 500 ppb. Consequently, the potential levels of thiol concentration generated by UV disinfection are safe even at the highest acceptable airborne dust level.

CONCLUSION

Given that human occupancy normally generates concentrations of dust well above 75 μg/m3 (0.000033 grain/ft3) and that this dust is mainly made of human dead skin and hair, which consist of keratin and cysteine molecules; and understanding that high energy UV-C photons can break-up these molecules into thiol molecules which have a very low smell threshold, this paper has revealed the root cause of the odor produced by UV disinfection9 of rooms. Given that the resulting potential concentrations of thiol molecules are negligible when compared to the published acceptable exposure limits, it is safe to enter a room after germicidal UV disinfection has been performed.

ACKNOWLEDGMENTS

The authors are grateful to Dr. Wladyslaw Kowalski for data and editorial assistance.

NOMENCLATURE

μg = micro gram

ppm = parts per million volumetric concentration

ppb = parts per billion volumetric concentration

nm = nanometer (10-9 m)

grain = lb/7,000

References

Spengler, Samet, McCarthhy, Indoor Air Quality Handbook. McGraw-Hill, 2001.

Fergusson,J.E.,Forbes,E.A.,Schroeder,R.J., The Elemental Composition and Sources of House Dust and Street Dust, Science of the Total Environment, Vol.50,pp.217-221, Elsevier, April 1986.

Pure Appl. Chem. 56 (5), 1984: 595–624, Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)”, doi:10.1351/pac198456050595.

C.R. Robbins, Chemical and Physical Behavior of Human Hair, DOI 10.1007/978-3-642-25611-0_2, # Springer-Verlag Berlin Heidelberg 2012.

UWaterloo, Bond Lengths and Energies. n.d. Web. 21 Nov 2010. http://www.science.uwaterloo.ca/~cch…20/bondel.html

EPA. Reference Guide to Odor Thresholds for Hazardous Air Pollutants Listed in the Clean Air Act Ammndments of 1990. EPA/600/R-92/047, March 1992.

Disinfecting Air & Reducing Ethylene in Cold Rooms

Disinfecting Air and Reducing Ethylene in Cold Rooms

Mold and bacteria can severely impact the quality of meat, chicken, fish, fruits and vegetables that may be stored or prepared in warehouses and cold rooms. Ethylene off-gassing causes fruits and vegetables to prematurely ripen and aged, dramatically shortening shelf-life.

Sanuvox UV IL-CoilCean systems installed facing the cooling coil are designed to bask the coil and air with ultraviolet energy destroying microorganisms including bacteria, mold and viruses while oxidizing and reducing ethylene off-gassing.

With its high efficiency patented air disinfection systems, Sanuvox offers the right solution when the objective is to destroy airborne bio-chemical contaminants (e.g. bacteria, viruses, mold) that may affect the storage and preparation of fish, chicken and meat, as well as destroy ethylene off-gassing that causes produce to ripen faster.

THE EQUIPMENT

Multi-IL CoilClean units are installed facing the cooling coils in the fan coil unit. Each IL unit includes a UV-C/UV-V lamp mounted in an anodized aluminum parabolic reflector. The ballast box incorporates LED status lights for providing lamp status and replacement and can be remotely monitored.

OPERATING THE EQUIPMENT

The fan coil unit recirculates the air where:
1. The UV-C germicidal section of the UV lamp destroys airborne biological contaminants (viruses, mold, bacteria and spores).
2. The UV-V oxidizing section of the UV lamp reduces ethylene, slowing down the ripening process of vegetables and fruits. Coils remain clean and more energy efficient.

SLOWING DOWN THE CONTAMINATION SPREAD WITH UV-C
Produce will degrade due to the rotting process that is caused by parasitic fungi and mold. Food deterioration begins with the breakdown of the cellular tissue by enzymatic action that allows the growth of microbes. Germicidal UV (UV-C) is extremely effective at preventing the reproduction of bio-contaminants because UV-C destroys airborne fungi, molds and spores, limiting the contamination spread from one fruit to another. Meat, fish and chicken are especially vulnerable to airborne biocontamination. UV-C sterilizes the air, destroying contaminants as they circulate within the cold room.

RETARDING THE RIPENING PROCESS WITH UV-V
Photo-oxidation with UV-V can be used to reduce chemicals that trigger the ripening of fruits and vegetables. The life stages of a plant are influenced by plant hormones. An organic compound involved with ripening is ethylene, a gas created by plants from the amino acid, methionine. Ethylene increases the intracellular levels of certain enzymes in fruit and fresh-cut products, which include:

  • Amylase, which hydrolyzes starch to produce simple sugars.
  • Pectinase, which hydrolyzes pectin, a substance that keeps fruit hard.

UV-V oxidizes and thus neutralizes the ethylene molecules released by the ripening process, slowing down the spread of ripening to the surrounding produce. This oxidation process breaks down ethylene into carbon dioxide and water vapor.
Ethylene C2H4 C2H4+ O* -> CO2 +H2O

WHERE TO INSTALL

Many buildings and facilities can be equipped with the IL-CoilCean systems, like cold storage rooms, groceries, meat, fish and chicken storage, preparation facilities, fruit and vegetable retailers, warehousing and transportation.

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Fruits & Vegetables Surface Disinfection

Fruits and Vegetables Surface Disinfection

Surface contamination of fruits and vegetables is a problem for growers, distributors and retailers. Mold and bacteria can have severe effects causing produce to spoil.

Sanuvox UV IL Food Safe purifiers for food products and their packaging are exceptionally safe and versatile disinfection systems for surface, packaging and conveyor applications designed to bask meat, fish, poultry, fruits and vegetables, baked goods and packaging with UV-C germicidal light. The UV system is extremely effective at destroying surface contamination while extending product shelf-life. Only a few seconds of exposure can achieve up to 99.9999% destruction of common biological contaminants that are problematic in the food industry.

Incorporate the UV fixtures into the production line (i.e. over the conveyor belts) to bask the products and surfaces prior to packaging, maintening a sterile product ready for distribution and consumption.

As the system is incorporated into the production line, the lamps are covered with Teflon, that will trap pieces of grlass in the event of breakage.

When the objective is to prevent and destroy microbial contamination, such as bacteria and fungi that occur naturally on fruit and vegetable surfaces, and are responsible for premature decay, Sanuvox offers the right solution with its high efficiency patented air purification system. The process will leave no residue as is found using chlorine or irradiation treatments with gamma rays. At the producer level, sterilization of fruits and vegetables could reduce the use of pesticides.

THE EQUIPMENT

IL Food Safe purifier for food products equipped with parabolic reflectors and Teflon coated lamps will be positioned equidistant across the conveyor, parallel to it. Computerized sizing programs taking into account the speed of the conveyor and the contaminant(s) to be treated will determine the size of the lamps.

Typical installation:

OPERATING THE EQUIPMENT

The end user will determine the location and design of the lamp assembly enclosure that will attach to
the conveyor guaranteeing there is no direct UV exposure to employees. Fruits and/or vegetables will be exposed for a predetermined period of time to UV light as they move through the enclosure on the conveyor. This predetermined time will be sufficient to sterilize the fruit and/or vegetable pathogens and slow down ripening process.

RESEARCH ON STRAWBERRIES
Researchers from the Department of Food, Science and Nutrition (Laval University, Quebec, Canada) demonstrated that exposing strawberries to ultraviolet light prolongs their shelf life. Freshly picked strawberries exposed to germicidal ultraviolet (UV-C) have retained their freshness for 14 to 15 days, while untreated freshly picked strawberries were “almost done” on the tenth day.

The conclusions from this research have been published in the Food Science Journal. Refrigeration, which slows the growth of microorganisms and fruit ripening, allows a limited but effective mean regarding conservation of strawberries.

“Exposure to UV-C is a very interesting approach to facilitate the marketing and distribution of fresh fruits and vegetables”, says researcher Joseph Arul. This treatment slows the ripening of strawberries: they remain firm longer, their respiratory rate is lower, their color is more attractive and the taste is not altered. “It is believed that exposure to UV-C would kill some mold on the surface of the fruit or, more likely, the treatment would stimulate the defense mechanisms of the produce,” suggests the researcher.

Arul’s team has already demonstrated the benefits of UV-C exposure for the conservation of carrots, broccoli, tomatoes and blueberries.

Arul does not anticipate negative reactions from consumers, unlike gamma irradiated food, or more recently, genetically modified organisms. “The technique is more acceptable to a consumer. In low doses, UV is beneficial. It is a light source and I do not think people have problems with that.”

WHERE TO INSTALL

Many facilities can be equipped with the IL Food Safe, like vegetable growers, fruit and vegetable importers, hydroponic producers, and value-added packagers.

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Sterilizing Air in Facilities

Sterilizing Air in Facilities

New buildings are built tighter to save energy, while older buildings are implementing new measures to reduce heating and cooling loss. Reduced fresh air also prevents dilution of contaminated air resulting in an increase of contaminants as they are now trapped inside and are continually recirculated throughout the space.

Indoor Air Quality (IAQ) applications in hospitals, schools, commercial buildings and offices vary. From Hospital Acquired Infection (HAls), sick building syndrome, absenteeism and work place productivity, Indoor Air Quality influences these facilities in many differents ways.

When the objective is to eliminate up to 99.9999% of airborne bio-contaminants, including viruses and bacteria that circulate through the ventilation system without increasing the pressure drop resulting from high efficiency filtration, Sanuvox offers the right solution with its high efficiency patented air purification system.

THE EQUIPMENT

The BioWall air purification unit is installed in the ventilation duct parallel to the airflow, allowing sufficient contact time that is required for airborne sterilization. The UV-C intensity of each lamp can be measured in “realtime” with an optional UV-C sensor, ensuring the required inactivation intensity will be delivered to the contaminant.

OPERATING THE EQUIPMENT

To create the sterilization chamber in the existing duct (up to 5 feet deep per unit), the walls are covered with an aluminum reflective material. The proprietary sterilization sizing calculations take into account: air velocity, dimensions of the duct, the UV lethal dose needed to sterilize the microorganism for the desired inactivation rate. The sizing calculations will determine the number and length of the BioWall unit(s) required. The optional UV-C sensor will guarantee that the UV-C emitted from the lamp will exceed the amount of UV-C that is required at all times.

UVC GERMICIDAL PRINCIPLE

The 254nm UV-C germicidal wavelength has been used for decades for sterilization and its effect on microorganisms is well documented. UV germicidal process inactivates microorganisms by damaging their DNA structure, making it incapable of reproducing. The germicidal efficiency can deliver virtually a 100% disinfection rate. The system can achieve exceptionally high disinfection rates as a result of the BioWall unit being mounted parallel to the airflow and the desired intensity is sized for each particular application.

WHERE TO INSTALL

Many buildings and facilities can be equipped with the BioWall unit, like hospitals, private clinics, veterinary clinics, as well as fertility centers. It can also be installed in schools, universities, offices towers and commercial buildings.

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