Calculation of the number of installations for air disinfection

Of greatest practical importance is the use of BUV lamps for disinfection and sanitation of indoor air with a large crowd of people: waiting polyclinics, group rooms of kindergartens, recreation rooms in schools, etc.

There are two methods of sanitation of indoor air with BUV lamps – in the presence of people in the room and in their absence. The most effective is air sanitation in the presence of people, since they are the main source of microbial contamination of indoor air. In this case, the air of the upper zone of the room is irradiated with shielded BUV lamps, which are placed throughout the room at least 2.5 meters from the floor in the places of the most intense convection air flows — above the door, windows, and heating devices. In this case, the lower layers of air are disinfected by convection. Shielding fittings direct the beam flux upward at an angle between 5 and 80 ° above the horizontal surface.

A type of shielded irradiator is air circulators, recommended for continuous irradiation of rooms in which people are constantly present and who have high aseptic requirements (operating, dressing rooms, sterile area of ​​the central sterilization department).

The power of bactericidal irradiation of BUV lamps depends on the electric power consumed by the lamp from the network. When determining the required number of bactericidal irradiators, it is assumed that 0.75 – 1 W of power is consumed per 1 m3 of the room’s volume .

Example. For air sanitation, a room with a volume of 90 m3 must be equipped with an installation with BUV-15 lamps. Air sanitation will be carried out in the presence of people. How many lamps are needed?

Decision. Under the given conditions, for the renovation of 1 m3 of air, 0.75–1 W of lamp power is needed, for the entire room volume, the total power should be 67.5–90 W. This requires 5-6 lamps BUV-1

67.5 W: 15 = 4.5; 90 W: 15 = 6

Sanitation of indoor air in the absence of people is used in bacteriological laboratories, operating rooms, dressing rooms, etc. after wet cleaning . Open, unshielded lamps are placed evenly throughout the room or predominantly above work desks. As a rule, a lamp is also placed above the door, creating a “curtain” of bactericidal rays. The number of lamps and the rehabilitation time depend on the mode (cleanliness class) of the room. The minimum number of lamps should be such that at least 1.5 W falls on 1 m3 of room, preferably 2-2.5 W of power consumed from the network.

Direct mercury-quartz lamps (PRC) are sources of ultraviolet radiation in regions A, B, C and in the visible part of the spectrum. The maximum of their radiation (25%) is in region B, 15% – in region C, in this regard, PPH lamps are used both for irradiation of people with preventive and therapeutic purposes, and for disinfection of environmental objects – air, water, etc.

The lamps are made of quartz glass and filled with a metered amount of mercury vapor and argon. In terms of power, the PRK lamps are divided into several types: PRK-2 (375 W), PRK-4 (220 W), PRK-7 (1000 W).

Two types of special fittings (irradiators) have been developed for PRK lamps:

                                    • for PRK-7 lamps , a large -output mercury-quartz beacon type irradiator , the column of which has a constant height; 

                                    • for PRK-2 and PRK-4 lamps, a beacon type mercury-quartz irradiator is small, the column of which can be of different heights. 

Sanitation of indoor air by radiation of PRK lamps can be carried out in the presence or absence of people. In the first case, the lamp is installed at a height of 1.7 m from the floor with a reflector directing the radiation up to the ceiling. For 1 m3 of the room, 2 – 3 W of power consumed from the network should fall .

During air sanitation in the absence of people, 5 to 10 W of power consumed from the network should fall per 1 m3 of air and the air irradiation time should be as long as possible.

Open (unscreened) germicidal lamps

they are used only in the absence of people — between work, at night, or at the allotted time — for example, 1-2 hours before starting work in the operating room. The minimum exposure time is 15-20 minutes. Open lamp switches should be placed in front of the entrance to the room and equipped with a signal inscription “Do not enter, the bactericidal irradiator is switched on”. It is FORBIDDEN to find people in rooms where unshielded lamps are turned on! Entrance to the room is allowed only after turning off the lamp, and a long stay in the indicated room – 15 minutes after turning off.

Shielded bactericidal lamps can work up to 8 hours a day. It is more rational to irradiate 3-4 times a day for 1.5–2 hours with breaks to ventilate the room for 30-60 minutes, since when the lamp is working, ozone and nitrogen oxides are formed, which irritate the mucous membrane of the respiratory tract. In recent years, ozone-free bactericidal lamps have been created, which is achieved through the use of special quartz glass that does not allow UV radiation shorter than 200 nm, which causes the formation of ozone.

Irradiation of air with PRK lamps is carried out for 30 minutes several times a day at intervals used to ventilate the room.

The average life of a bactericidal lamp BUV is 1,500 hours, PRK lamps – 800 hours. It is necessary to take into account the duration of each irradiator in a special journal, fixing the time the lamp is turned on and off. It is forbidden to use bactericidal lamps with an expired shelf life.

Strict adherence to the regimen for the use of bactericidal lamps is important, since the boundary between the positive bactericidal effect of UV radiation and the negative one associated with the selection of resistant microflora under the weak influence of UV rays is not sufficiently distinct.

UV rays are effective at a distance of no more than two meters and with a relative humidity of 40 to 70%; at higher humidity, their bactericidal effect is reduced. On dark surfaces treated with UV rays, 10–20% more microbes remain than on light surfaces under the same conditions. In the shade, for example, under the table board or on the back of the instrument, ultraviolet radiation does not work.

Errors entailing negative epidemiological consequences include:

• Failure to comply with prescribed exposure regimes; 

• mismatch of type (open, closed) and the number of emitters to the needs of sanitation; 

 • neglect of the “age” of the lamps, with an increase in which their bactericidal activity significantly decreases; 

 • surface contamination of lamps; 

 • “exaggerating the expectation” of the effectiveness of ultraviolet irradiators, which contributes to neglecting other, no less reliable ways to rehabilitate the premises – ventilation, cleaning, “rest” of the operating room, treatment with chemical disinfectants, and increased ventilation efficiency. To assess the bactericidal efficacy of specific irradiators, bacteriological studies of the air and washings from surfaces before and after irradiation are carried out. Remediation is considered effective if, after irradiation, the number of microorganisms in 1 m3 of air has decreased by 80% or more. 

event_note August 11, 2019

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