Minnesota Department of Corrections


Division Directive:     500.522                       Title:   Negative Pressure Isolation Rooms

Issue Date:                 7/3/07

Effective Date:          8/7/07


AUTHORITY:           OSHA Directive CPL 2-106

MNOSHA Instruction CPL 2-2.48


PURPOSE:    To separate offenders who have suspected or confirmed infectious tuberculosis (TB) from other persons; to provide an environment that allows reduction of the concentration of droplet nuclei through various engineering methods; and to prevent the escape of droplet nuclei from such rooms into the corridor and other areas of the correctional facility using directional airflow.


APPLICABILITY:    Facilities with negative pressure isolation rooms.


DIRECTIVE: The department will keep offenders with suspected or confirmed infectious TB disease in isolation rooms under negative pressure to induce air flow into the room from all surrounding areas (e.g., corridors, ceiling plenums, plumbing chases, etc).



Negative pressure – the minimum pressure difference necessary to achieve and maintain negative pressure that results in airflow into the room is 0.001 inch of water.



A.        Monitoring Negative Pressure Isolation Rooms When In Use

1.         Begin monitoring immediately prior to or upon the isolation of an offender with suspected or confirmed infectious TB.

2.         Monitor daily

3.         The supervising lieutenant/designee will conduct daily testing using one of the following procedures.  The supervising lieutenant/designee will

a)         Ensure the offender in the room is wearing a surgical mask.


b)         Hold non-irritating smoke near the bottom and approximately two inches in front of the door, or at the face of a grill, or other opening if the door has such a feature.  Generate a small amount of smoke.  The smoke must be held parallel to the door, and the smoke must be issued slowly to ensure the velocity of the smoke does not overpower the air velocity.  If an anteroom exists, the direction of the airflow must be tested at the inner door between the isolation room and the anteroom.


c)         Move the smoke generator along the bottom of the door.


d)         Ensure the room is under negative pressure, by observing the smoke traveling under the door and into the room.  If the room is not under negative pressure, the smoke will be blown outward or remain stationary.


4.         Staff will check the pressure differential gauge daily (if equipped with) and document it on the room log with the date, time, and initials.


B.        If the room is not under negative pressure, and cannot be repaired within six hours, transport staff will transport the offender to an appropriate regional medical center, or department negative pressure isolation room. The offender must continue to wear the mask until repairs are completed, and a successful smoke test is achieved.


C.        Monitoring Negative Pressure Isolation Room When Not In Use.

The unit supervising lieutenant/designee will

1.            conduct monthly non-irritating smoke tests utilizing the procedure described in section A above.


2.         document results on the Negative Pressure Isolation Room Log.


D.        If the room is not equipped with an anteroom, the facility safety officer will develop instructions to minimize entry of contaminated air to the corridor.  Instructions may include, but are not limited to, minimizing entry into the room, adjusting the hydraulic closer to slow the door movement, and reduce displacement effects.


E.         Staff must ensure that air exhausted from the rooms is safely exhausted directly outside, and not recirculated into the general ventilation system.  If not exhausted through a HEPA filter, the air must be exhausted away from intake vents, operable doors and/or windows, and sidewalks.


F.         Communication of Hazards:  Staff will

1.         post instructions on the door, including:

a)         the signal word, “stop”

b)         airborne isolation

c)         a description of the necessary precautions to take


2.         label ventilation system components that transport contaminated air with a biological hazard label.


3.         identify and label circuit breakers to prevent unplanned shutdown of the dedicated ventilation system.


G.        Cleaning Rooms in Use:  Staff will:

1.         use an EPA approved germicide or disinfectant in the routine daily cleaning of isolation rooms.

2.         follow isolation practices while cleaning these rooms.

3.         allow the offender, when appropriate, clean his/her room.

4.         wipe down cleaning equipment used in the room with an EPA approved germicide or disinfectant before being reissued.


H.        Cleaning Vacated Rooms:  Staff will:

1.         ventilate the room in accordance with the Air Changes Per Hour Chart (attached) to achieve 99.9% efficacy in removing airborne contaminants.

2.         document above in the Negative Pressure Isolation Room Log.

3.         after proper ventilation (described in H.1.), allow area offender cleaners to complete the final clean-up using an EPA approved germicide or disinfectant without using special personal protective equipment other than that required by normal usage of the cleaning chemical.


I.          Recommended Equipment

1.         Outside the room

a)         Safety officer approved respirators; and

b)         Contaminated linen hamper with lid (soiled linen and waste must be handled using standard precautions).


2.         Inside the room

a)         Garbage holder for contaminated waste;

b)         Plastic aprons or gowns; and

c)         Disposable gloves.


J.         All staff entering an air borne isolation room must wear a National Institute of Occupation Health and Safety (NIOSH) respirator with a minimum filtering efficiency of N-95.  The staff wearing respiratory protection must be medically certified and trained.  Staff wearing tight-fitting negative pressure respirators must have successfully completed a fit test.  Only trained essential staff may enter the room.


REVIEW:       Annually


REFERENCES:         Morbidity and Mortality Weekly Report “Guidelines for preventing the transmission of mycobacterium tuberculosis in health care facilities,” 1994

Center for Disease Control “Controlling TB in correctional facilities.”


SUPERSESSION:     Policy 500.522, "Negative Pressure Isolation Rooms," 12/6/05.

All facility policies, memos, or other communications, whether written or transmitted by electronic means regarding this subject.


ATTACHMENTS:    Negative Pressure Isolation Room Test Log

Air Changes Per Hour Chart



Nanette M. Larson, Director

Health Services



500.522OPH, “Negative Pressure Isolation Rooms”