Merge branch 'ad-BSC-good-practices' into 'develop'

Update file utilization-of-bsc.md

See merge request !522

external/lab-equipment/utilization-of-bsc/utilization-of-bsc.md

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   - /cards/lab:utilization-of-bsc
   - /external/cards/lab:utilization-of-bsc
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+ 
 # Biosafety Cabinets: good practices
 
 To ensure a good work quality in a sterile and safe environment, it is essential to know how to work in a BSC and what are the best practices.
@@ -89,17 +90,17 @@ Corrosive chemicals such as bleach should be avoided, but if used, should be fol
 
 ## UV lights
 
-Extract from Environmental Health and Safety, University of Washington: *The trouble with UV light in your biosafety cabinet*.
+Some of the biosafety cabinets are equipped with UV lights. You may want to turn them on or to ask to install UV lights on your cabinet. 
+**Please note that we do not recommend the usage of UV lights in biosafety cabinet.** 
+The efficiency of UV lights in Biosafety cabinet is very limited. Everything in the shadow of a tips box, pipette holder,... will not receive any photon from the UV. 
+The surfaces below the worktop of the biosafety cabinet are also in the shadow.
 
-You may want to turn on the UV lights. If so, be aware that it may not be as effective for sterilization/decontamination purposes as you need it to be.
-Indeed, ultraviolet radiation is a form of non-ionizing radiation, and biological effects from it vary with wavelength, photon energy, and duration of exposure. The 100-280 nm wavelength band is designated as UV-C, which is used for germicidal purposes.
+Among the additional reasons why we do not recommend UV lights:
 
-The sterilization/decontamination activity of UV lights is limited by a number of factors, including:
-
-- **Penetration** In the dynamic air streams of BSCs, microorganisms beneath dust particles, plastics, and work surfaces are not affected by the UV light because it cannot penetrate particles so far from the UV source.
-- **Relative humidity** The germicidal effects of UV light drop off precipitously when relative humidity is above 70%.
-- **Temperature and air movement** The optimum temperature for the UV lamp to be effective is 25-27°C. Temperatures below this range result in reduced efficacy, and air movement can exacerbate this. 
-- **Cleanliness** Dust and dirt block the germicidal effectiveness of the UV lamp, so weekly cleanings are necessary.
-- **Age** Check UV lamps every six months to assure proper function, as the amount of germicidal wavelength emitted decreases with bulb age and hours of use.
-- **Overuse** UV lights are routinely left on overnight or longer in an effort to decontaminate workspaces, but this practice can result in the germicidal wavelength no longer being produced by the bulb.
-For these reasons and environmental concerns, it is not recommend to use the UV lights in BSCs. Retrofitting any equipment (e.g., UV lights) into a cabinet may alter the air flow characteristics, invalidate the manufacturer warranty, and is not recommended.
+- UV lights efficiency decreases with the square of the distance, making it inefficient where it would be the more interesting to have it.
+- UV lights efficiency decreases with the age of the light bulbs.
+- UV lights affect plastics lifetime and may damage items left in the Biosafety cabinet
+- Dust and dirt protect "bugs" from UV light.
+**=> UV lights can not replace cleaning and disinfection.**
+ 
+Would you experience contamination issue or have doubts about good practices in your laboratory setup, create a ticket to get in touch with our biosafety officer that can help you to review your procedures and look at the laboratory setup.