Published:  01:23 AM, 11 August 2020 Last Update: 01:30 AM, 11 August 2020

UV technology to deal with Covid- 19 - II

Available with various levels of automation.  With timers for setting irradiation time or remote controlled or both, depending on the manufacturer. Motorised versions are operated with a operator walking behind (with full UV protective equipment /clothing).

As he walks down a corridor of a hospital/airport/bank/office/room, the wall, floor, and glass partition whatever is exposed gets sterilised within the short exposure time of a few seconds due to selecting of a High Power UV. The areas being covered must be free of people.

Lower power versions (15 to 65 W) are hand held (much like a lantern) , battery or mains power, with timer . Operation is simple , take it to a room you want to sterilise  set the timer,  set lamp on, leave the room , and you are done. An indicative size would be 100 to   150 W UV output for a 20-25 ft room (~400-600W power) depending on the quality and manufacturer.

Low and medium power models (50- 100W ) are available in free standing and movable  and with angle set , i.e. instead of vertical, the UV  light bulb angles can be varied from vertical to horizontal, increasing its versatility. 

The surface irradiators would be suitable for OT's, post ops, Patient rooms/cabin/ward, hotel rooms, sitting room in banks/ waiting room / doctors' chamber or any spaces etc. There is however one big disadvantage in that it can only be operated in unoccupied areas.  The irradiation is short, 10-20 min or less, which should not be a problem.

However Room sanitizer, fan type, plus Surface irradiator combination should be the aim in OT's, post ops, ICU's etc requiring high level of cleanliness and protection.  The fan type sanitizer is run continuously (as required) and the surface type at intervals to back it up.

Advantage & Disadvantage

Inspite of the many limitations, the UV C systems has benefits as well.   Disinfection times are short, typical for a room being 15-20 min, which allows for quick turnover for hospital rooms /wards other spaces etc. All surfaces within a certain distance exposed to, with the proper power and time will give an assured level of  disinfection without any residue.

Some thoughts on local applications:

1) As previously mentioned, the UV equipment are relatively simple in its construct. Some applications warrant local input and adaptation.  There are scores of applications which can be thought of by organisations satisfying their individual needs.  Some of the more general  application  which comes to mind are mentioned here.  

i.UV sterilization for Hospital Staff gowns, overall, labcoat, masks and gloves etc etc. One of the more difficult things in a hospital clinic surrounding is to maintain cleanliness of the above mentioned items;  besides the physical cleanliness which can be achieved by washing; the items have to be made virus ( and also bacteria ) free.

One can UV sterilize the items once, twice or even thrice every  shift for the nurses and doctors and other staff. There is no way one can wash three times a shift, not  physically, not economically possible . What do you do. You UV Sterilize. In the paragraphs  below , I will try to highlight the ways it  may be approached.

Equipment/ facility required

a. General Floor model  UV C, lamp non Ozone, about 4 feet long and not less than 35W , 66W UV power( not total power)  .  If a commercial one is not available at hand, have one made.

b. UV eye protection goggles /specs and face cover and leather gloves. All are UV protection items, to be used by the operator  for regular use.

c. Enclosed space  for  UV sterilizing .  The space may be a very small room or if one is not available , wooden box may be  made or a table may be used.

The procedure is simple, hang or lay the coat/items  and  irradiate both the sides. The proper dose must be given. This dose will depend on the light intensity and what time (sec) it is exposed. If the object is held at 50 cm from the UV bulb, it will require more time than if it were placed at 15 cm.  A 33W (UV power not total power ) will  require around 5sec  for  sterilization if held at  at 10 cm  and 18-20sec if held at 30cm .

It make sense to bring the items as close as physically possible to reduce irradiation time . The figures here  is to give an idea and will depend on the length of the tube and other factors.   It will kill 99.99 %, that is as  clean  as it can get.

It is very relevant to understand the principle of UV sterilization. The UV light has to shine onto the surface in order to work, if it is in the shade or the light is obstructed, it will not  sterilize those areas.Thus the need to flip over any items to be sterilized or expose both sides simultaneously.

If you decide to irradiate the garments in a hanging position, with UV bulb on both sides, irradiation time is reduced i.e. halved . Same process for masks, gloves etc, PPE in general.

The UV provides a residue free disinfection, so there is no concern over residues which has to be wiped or removed, no chemicals added or need to be removed.Though it appears quite simple, but is NOT to be taken casually. UV light though may look nice blue in colour, is dangerous for the uninformed .

Proper precautions have to be taken and procedure set up to carry out normal sterilizing.  "WARNING "signs put up when a room is being irradiated.Purpose (as above) specific fixture if not available can be built around the principles highlighted in these paragraphs. Help could be sought from persons /institutions. 

ii. UV sterilizing of  cabin/ ward  room and beds, pillows

Commercial models are available on movable stands, where the tubelight_like fixture can be  varied in the angle, from vertical to 90 degree horizontal, i.e. parallel to the ground.

1.  General sterilization of a cabin /ward / room.      

2.  Sterilzation of  bed/pillows/ PPE/ masks / chairs/other items For  room sterilization  the lamp fixture  is stationed on one end of the room , suitably placed to throw the UV light on as large an area as possible , the furthest area ( and the UV lamp power ) will determine the irradiation time.  The highier the UV power , the lesser the time of irradiation. The fixtures  normally have built-in timers , to set the time,15, 20, 30 min   so on.

Reminder again : whatever gets/receives the light gets irradiated . If certain area of the room is not covered, the lamp may be repositioned for another round of irradiation. Most manufacturers will recommend  the area coverage. With400W of UV power (not electric power) a  wall 20 ft away will require about  15-20min, this implies that anything nearer  will  get sterilized  much earlier.

Bed/blanket/ pillows for UV sterilization: UV has a distinct  advantage over others, as bed, mattress and  most pillows can't be otherwise cleaned, washed . The same fixture as above is used , but now the UV tube-light is brought parallel to the ground (turn 90 deg from vertical)  and over the bed at a distance to ensure good  overall coverage by the UV light. Now the bed being near to lights (say 30cm) will  take  much less time.

For instance with a 40W UV power and a distance of 10 cm , the calculated time comes out 5sec, so considering all other unforseen inefficiencies, a half minute irradiation is all it takes for the top half and another 30sec  for the bottom half of the bed.

Pillows have to be turned over to properly disinfect. In all likelihood all pillows will be done in a separate batch iii . Bank, Airport sitting , and office Counters  :  Bank counters , office partitions, airport corridors, walkways, sitting rooms  are ideal candidates  for surface irradiation.
Existing central   air-conditioning systems in hospitals It is a practice in many hospitals or even commercial buildings in the West (even before Covid ) to have the air conditioned air  to be UV  cleaned before it is supplied to the individual rooms.  This is done to avoid fungus and moss and other bacterial build- up in the duct systems which even impedes the air flow.  Such systems now can be definitely installed here, but understandably will require capital expenditure.

For existing central airconditioning systems it is pertinent to point out the fact that : if a part of the hospital (few rooms /ward)  has been separated for COVID area, and if it is under the coverage of central air condtioning, it must be ensured  that the return- air  from these areas  are  NOT mixed with the return air from Non Covid areas, but  exited out and preferably after some filtration.  This is otherwise also known as Once Through System and is used in many radio active facilities as well.   

Doctors , nurses and medical staff  come to face  patients ,  Covid or otherwise need  to preserve the viral and bacterial cleanliness of their  PPE /garments etc, it is unlikely to be  immediately thrown away . They need not be thrown away. UV sterilize them.         
                                                                                                                                      Fixtures  have to be constructed  to carry out the sterilization of PPE (lab coats, overall etc) in a quick and safe manner. Safe to those around and to the operator. It must be seen that there is no leakage , reflection of UV rays  to the operator and general public.  Procedures will have to be thought of for irradiating  beds /pillows and other specific items and fixture constructed all these with at least mid level participation and not delegated to  technicians.

In Conclusion
UV sterilization is an excellent tool particularly in the present day context and relatively cheap.  Procurement is one third the work. Developing procedures is very important for effectiveness and safety, due effort has to be made in this regard.     (Concluded)

Tanbirul Quadir Choudhury is retired Chief Engineer, BAEC, Dhaka.

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