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indoor air quality |
Question:
Which are the suggestions for an useful and representative microbiological air sampling in indoor environment?
Answer:
The reported suggestions are elaborated from a table of the “Sampling and Analysis of indoor microorganisms” book written by C. Yang and P.Heinsohn. Wiley Publications.
-The equipments and material
“DUO-SAS-360”, microbiological air sampler with twin aspirating chambers
“Daily-Head” sterile aspirating heads
“Telesco” Tripod for air sampler
“Agar Contact” Contact Plate with Tryptic Soy Agar medium for total bacterial count
“Agar Contact” Contact Plate with Sabouraud Dextrose Agar medium for mould and yeast count
| 1 | Number of indoor air sampling locations | One location for 200 cubic metres of floor space unless room sizes are smaller | | 2 | Placement of air sampling equipment within room | Central to room to the extent possible; > 1 metre away from an exterior wall; away from plants. On a tripod approximately 150 cm above finished floor | | 3 | Number of outdoor air sample locations for single-story, non-mechanically ventilated buildings | At least two, front and back of the building; tripod should sit on concrete or asphalt, if possible, and away from plants | | 4 | Number of outdoor air sample locations for multiple-story, non-mechanically ventilated buildings | Two grade level at front and back for at least the first five stories; tripod should sit on concrete or asphalt, if possible, and away from plants | | 5 | Number of outdoor air sample locations for multiple-story, mechanically ventilated buildings | At air intake of the air handling unit supplying the area(s) of interest. Tripod should sit on concrete or asphalt, if possible, and away from plant | | 6 | Sampling plan | Although there are no generally recommended guidelines, at least two total bacterial counts and two moulds counts should be collected at each location. The reason for collecting two of each kind of sample is to have more data from the same location to assess the true mean of that airborne concentration at that location at the point in time. The recommendation is to collect a pair of sample simultaneously (total bacteria from an aspirating head and total fungi from the other one), followed immediately by a second such pair. | | 7 | Microbiological methods | Total bacterial count with TSA medium (25 and 37°C) and Total fungal count with SDA medium (30°C)
Isolation and identification to the species level on request | | 8 | Air samplers, air flow rate, time | “DUO-SAS-360” air sampler
Air flow rate 100 litres/minute
Volume 1000 litres of air for reach cycle |
Question:
Which are the microbiological parameters to evaluate in the indoor office premises using the “SAS” air sampler?
Answer:
-Introduction
Three are the parameters that should be investigated:
Psycrotrophic Total Bacterial Count
It is an indicator of the environmental bacterial contamination. In fact the psycrotrophic bacteria have an ideal growing temperature of about 25°C (15°-30°C) and they use the organic material present in the soil, vegetables and prefer humid environments.
Mesophylic Total Bacterial Count
It is an indicator of animal or human contamination. In fact the mesophylic population has an ideal growing temperature of about 37°C (25°-40°C) and also includes the traditional pathogens.
Moulds and Yeasts Total Count
It is an indicator of the poor quality of indoor ventilation (air conditioning, heating, filters).
-The European Index
The European Collaborative Action Report No.12 (1993) gives the following reference index:
Total Bacterial Count
| Bacterial Population | CFU/cubic metre
Industrial Environments | CFU/cubic metre
Non Industrial Environments | | Very Low | < 100 | < 50 | | Low | < 500 | < 100 | | Interm. | < 2,500 | < 500 | | High | < 10,000 | < 2,000 |
Yeast and Mould Count
Yeast and Mould
Population | CFU/cubic metre
Industrial Environments | CFU/cubic metre
Non Industrial Environments | | Very Low | < 50 | < 25 | | Low | < 200 | < 100 | | Interm. | < 1,000 | < 500 | | High | < 10,000 | < 2,000 |
-Microbial Identification
It is necessary in some cases to perform the microbial identification. Examples are Legionella or moulds (Cladosporium, Penicillium, Aspergillus, Fusarium, Cryptococcus neoformans).
-The instrumentation for the microbiological sampling of air
It is used the “SAS ISO”.
Question:
Which is the difference between the microbial air sampler SAS Super and SAS IAQ? Answer: The SAS Super IAQ is a microbiological air sampler especially suited for the Indoor Air Quality. It is based on the same working “impact” principle of the portable “Surface Air System” samplers, to perform microbiological evaluation of the air using “contact plates” or “Petri” dishes.
WORKING PRINCIPLE AND USE
Unscrew the drilled head and place a contact plate or a Petri dishes filled with medium ("Surfair Plate" or "Agar Contact Blister") into the housing. The environmental air is aspirated over the agar surface of the plate and airborne particles are captured on the agar by impaction. The quantity of air depends on the microbiological quality of the environment to be tested. At the end of the preset sampling cycle remove the plate and incubate it according to specific conditions (temperature/time). The number of CFU are then counted.
The SAS IAQ in comparuison with SAS Super 100 has less parameters and performances that are not necessary in the Indoor Air Quality evaluation. | | | | | |
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