|

Look for links to printable pdf
literature in equipment specifications sections, above in this column, & on
site map.



| |
Establishing
Airborne infection isolation rooms (AIIR)
& Protective Environments
(commonly referred to as negative pressure
& positive pressure isolation rooms)
Airborne infection isolation room
(AIIR). Formerly, negative pressure isolation room, an
AIIR is a single-occupancy patient-care room used to isolate persons with a
suspected or confirmed airborne infectious disease. Environmental factors are
controlled in AIIRs to minimize the transmission of infectious agents that are
usually transmitted from person to person by droplet nuclei associated with
coughing or aerosolization of contaminated fluids. AIIRs should provide negative
pressure in the room (so that air flows under the door gap into the room); and
an air flow rate of 6-12 ACH ( 6 ACH for existing structures, 12 ACH for new
construction or renovation); and direct exhaust of air from the room to the
outside of the building or recirculation of air through a HEPA filter before
returning to circulation (MMWR
2005; 54 [RR-17]).
Protective Environment (PE).
A specialized patient-care area, usually in a hospital, that
has a positive air flow relative to the corridor (i.e., air flows from the room
to the outside adjacent space). The combination of high-efficiency particulate
air (HEPA) filtration, high numbers (>12) of air changes per hour (ACH), and
minimal leakage of air into the room creates an environment that can safely
accommodate patients with a severely compromised immune system (e.g., those who
have received allogeneic hemopoietic stem-cell transplant [HSCT]) and decrease
the risk of exposure to spores
produced by
environmental fungi. Other components include use of scrubbable surfaces instead
of materials such as upholstery or carpeting, cleaning to prevent dust
accumulation, and prohibition of fresh flowers or potted plants.
Engineered specifications for positive and negative pressure rooms*
| |
Positive
pressure areas (e.g., protective environments [PE]) |
Negative
pressure areas (e.g., airborne infection isolation [AII]) |
| Pressure
differentials |
> +2.5 Pa§ (0.01″
water gauge) |
>
-2.5 Pa (0.01″
water gauge) |
| Air changes
per hour (ACH) |
>12 |
>12
(for renovation or new construction) |
| Filtration
efficiency |
Supply: 99.97% @ 0.3 μm DOP¶
Return: none required** |
Supply: 90% (dust spot test)
Return: 99.97% @ 0.3 μm DOP¶
^ |
| Room airflow
direction |
Out to the adjacent area |
In to
the room |
| Clean-to-dirty
airflow in room |
Away from the patient (high-risk patient,
immunosuppressed patient) |
Towards the patient (airborne disease
patient) |
| Ideal pressure
differential |
> + 8 Pa |
> - 2.5 Pa |
-
* From Table
6, full-text version,
"Guidelines
for Environmental Infection Control in Health-Care
Facilities", U.S. Department of Health and Human Services, Centers for
Disease Control and Prevention (CDC), Atlanta, GA 30333,
Published: 2003. See original document at above link, for
references.
-
§ Pa is the abbreviation for
Pascal, a metric unit of measurement for pressure based on air velocity; 250
Pa equals 1.0 inch water gauge.
-
¶ DOP is the abbreviation for
dioctylphthalate particles of 0.3 μm diameter.
-
** If the patient requires both
PE and AII, return air should be HEPA-filtered or otherwise exhausted to the
outside.
^
HEPA filtration of exhaust air from
AII rooms should not be required, providing that the exhaust is properly
located to prevent re-entry into the building.
Ventilation
requirements for areas affecting patient care in hospitals and outpatient
facilities
Further information:
-
Guideline for Isolation Precautions: Preventing
Transmission of Infectious Agents in Healthcare Settings,
CDC, June 2007
-
Guidelines for Environmental Infection Control in Health-Care Facilities,
2003
-
Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in
Health-Care Facilities, 1994
-
OSHA
Safety and Health Topics, Healthcare Facilities
-
Guidelines & Recommendations for Ventilation, Construction, and Renovation of
Hospitals
-
Isolation Rooms & Pressurization Control pictorials,
Penn State University
Architectural Engineering Indoor Environment Center
|