Sampling Critical Environments
By Andrew Streifel, Hospital Environmental Specialist, University of Minnesota
From Bioscience World, Summer 2009
CERTAIN HOSPITAL ROOMS provide a safe air quality environment for patients with suppressed immune systems. Air sampling for fungi is part of a process to validate the cleanliness of certain patient care areas.
The critical environments, such as
a Bone Marrow Transplant Room or
Surgery Suite, should provide a safe
environment with minimal presence of airborne microbes.
While there isn’t a standard relating
to hospital air quality, there are
ISO Standards that can serve as a
guideline. Once the hospital is occupied, the maintenance of low levels of
air quality becomes a challenge without focused control measures. (For
information on acquiring the ISO Standards, contact Bioscience
We need to assure an environment free of environmental infectious agents, such as, Aspergillus species and other fungal organisms capable of causing Aspergillosis, Aspergillus fumigatus, A. flavus, A. niger, A. nidulans and other opportunistic fungal species.
We look for these fungi using
selective media and an air sampler.
The SAS Air Sampler is used to compare
outside with inside microbial air quality. The tendency is to sample for fungal spores. The culture method is
preferred because visual identification of fungal spores is indistinguishable when they are small and round.
The size at 2-4 microns looks like a variety of species, which range from Gleocladium, Penicillium to Aspergillus
The use of the air and surface sample
capability will provide assurance
of air and surface microbial sanitation.
Often microbes found on surfaces
end up in air samples.
Interpretation guidelines for such
evaluations need to be established
before sampling begins. Opening of
bone marrow units have been
delayed because of environmental contamination found on the floors and in the air.
After the cleanest samples are
taken, move to similar area (with
HEPA if bone marrow transplant),
lobby area and outside for those comparisons.
Typical data in Minneapolis MN in summer can be seen in the chart below.
Outside data varies greatly depending on area climate (desert, agriculture, urban or forest), so results require a ranking of the samples demonstrating the cleanest area where the controls area greatest have
the lowest counts. This would rank
the BMT unit as best air quality with
the lobby being the least controlled.
The data below would be typical of an unoccupied area while the Nurse area would be high because it is occupied with minimal control. (An expanded version of this article may be requested from Bioscience International).
|Nurse area medicine||21||2100||na||na|
- Colony forming units per cubic meter
- Particles per cubic foot at >0.5 micron diameter
- Pressure in inches water column
Andrew J. Streifel, MPH,
|For thirty years, Mr. Streifel, Hospital
Environmentalist at the University of Minnesota Department of Environmental
Health and Safety, has published and
lectured extensively and served over 200 hospitals worldwide on air quality and
patient care environments for solid organ and bone marrow transplant areas. Appointed to the Revision Task Force American Institute of Architects Guidelines for Construction of Hospitals, he assists industry leaders in design of critical care environments.
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