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Microflora of the indoor air.
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Microbial contamination of the air is of great epidemiological importance as air is the most common medium through which airborne and droplet infections, including dust borne infections, are transmitted to a person. In case of airborne and droplet infections, such as influenza, acute respiratory diseases, tonsillitis, diphtheria, etc., bacterial contamination occurs as small particles of saliva and sputum get into the air when a person coughs, sneezes or speaks. Dustborne infections are transmitted when inhaling airborne dust which forms as infected droplets released from human respiratory passages get dry. Airborne dust which is found in the air remain infective for 2 – 3 hours, however, some viruses, such as influenza virus, diphtheria rod, etc., have been proved to survive for 3 – 4 months. Dust and bacterial contamination of the air is interdependent: great amounts of dust in the air can rapidly increase bacterial contamination of the air. Thus, if the air has been cleaned up, the bacterial contamination of the air decreases.
The degree of bacterial contamination of the indoor air depends on air exchange, sanitary conditions of the room, number of people in the room, observation of the rules of personal hygiene, etc. These factors should be well considered in patient care institutions when receiving inpatients. No more than 750 microorganisms per 1 m³ should be in the air in summer and 150 – in winter. The indoor pure air should contain no more than 1500 microbes per 1 m³ in summer, however, in winter these amounts should be no more than 4500 per 1 m³.
Table 2
Permissible levels of bacterial contamination of the air in in-patient clinics
| Room | Number of colonies в 1 м3 air | Content of Staphylococcus aureus in 1 м3 of air | Content of Gram-negative bacteria in 1 м3 of air |
| Operating rooms having 10-20 or more air changes (prepared to be used) | No more than 100 | None | None |
| Resuscitation wards | No more than 1000 | No more than 4 | None |
| Isolation wards/cubicles (before patients have been accommodated in them) | No more than 50 | None | None |
| Isolation wards/cubicles (when patients have been accommodated in them) | No more than 250 | No more than 1-2 | No more than 1-2 |
| Medical treatment room (before use) | No more than 50 | None | None |
| Medical treatment room (when used) | No more than 2000 | No more than 1-2 | No more than 1 |
Bacterial contamination of the air, especially if it is increasing is considered to be a sign of poor sanitary conditions.