Using UVC for TB Control
Efficacy of UVC for Tuberculosis (TB) Control
Airborne transmission of Mycobacterium tuberculosis and other
infectious agents within indoor environments has been a recognized hazard
for decades. Engineering controls such as ventilation and negative
pressure have been helpful for control of tuberculosis (TB) transmission
in high risk settings such as hospital isolation rooms. Increasing costs
associated with providing ventilation has prompted renewed interest in
other means to remove airborne infectious agents from room air, such as
the application of ultraviolet germicidal irradiation (UVGI). One
application of UVGI is to irradiate the upper part of a room while
minimizing radiation exposure to persons in the lower part of the room.
Data has been available showing that UVGI has the potential to be a useful
engineering control for TB. The 1994 CDC TB Guidelines (Centers for
Disease Control and Prevention, 1994) relied primarily on upper room air
UVGI studies over 30 years old when guidelines were written for its use as
an engineering control measure to mitigate the transmission of airborne M.
tuberculosis. Knowledge gaps still remained in regard to the impacts of
environmental factors such as air mixing, relative humidity and various
other parameters on the efficacy of upper-room air UVGI. In addition, no
room studies had been conducted using modern UVGI fixtures and bulbs. Thus
questions still remain on the best approach to install UVGI in real
settings. The aim of the study was to systematically investigate the
conditions under which UVGI can be expected to mitigate the spread of
tuberculosis. Completion of this work has significantly improved our
fundamental understanding of the efficacy of upper room air UVGl systems
and will facilitate their design, optimization and implementation on a
for TB Control/PDF/
TB is transmitted through the air. A person with TB disease of the lungs or
larynx can release droplets containing Mycobacterium tuberculosis (M. tb) into the air
by coughing, sneezing, talking, or breathing. These droplets, called droplet nuclei, can
cause TB infection if inhaled by anyone who shares air with the person who has TB.
Ultraviolet Germicidal Irradiation - UVGI
Ultraviolet Germicidal Irradiation -
UVGI is the use of a type of UV radiation, known as UVC, which has been
shown to kill
or inactivate M. tb in air. Ultraviolet Germicidal Irradiation - UVGI is generated by specially designed
using uvc lamps
that often look something like a fluorescent light. There are two ways that
UV lamps are
used in TB control:
• Upper-room UVGI is the use of Ultraviolet Germicidal
Irradiation lamps directly in a room where there is
risk of M. tb being transmitted. It is a useful infection control technique
spaces that may be occupied by a person with TB, such as prison day rooms,
homeless shelters, and waiting rooms.
• In-duct UVGI is the use of UVGI lamps inside an air duct or air cleaner to
air before it is recirculated. It is a useful upgrade for mechanical systems
air from high-risk congregate areas that may be occupied by a person with
TB. However, in-duct UVGI is not equivalent to direct exhaust or high
particulate air (HEPA) filtration for isolation rooms and high-risk
Upper-room UVGI uses lamps mounted at an elevation of seven or more feet.
are designed so that upper-room air is irradiated and disinfected. Cleaned
mixes with the air in the lower part of the room and dilutes infectious
Radiation levels in the lower parts of the room should be measured to verify
are within recommended parameters.
Care should be taken in the design, installation, and maintenance of
because of safety concerns. Also, effectiveness can vary and every
installation is unique.
In-duct UVGI uses lamps mounted inside a duct perpendicular to airflow. An
designed, installed, and maintained in-duct UVGI system should effectively
most recirculated air. This will therefore significantly increase the
effectiveness of the
recirculating mechanical ventilation system in reducing the risk of M. tb
The UV intensities of lamps used inside a duct can be, and should be,
lamps used for upper-room UVGI. This is because the risk of UV overexposure
For a given airflow, the number and spacing of the lamps is selected to
ensure that air in
the duct is exposed to sufficient radiation. The exposure depends on the
intensity of the
radiation and the time of exposure.
A duct access door should be provided so that the lamps can be cleaned,
replaced. To prevent exposure to the lamps, electrical interlock should shut
off the lamps
whenever the duct access door is open.
In-duct UVGI is also used in self-contained air cleaning units.
UVGI can cause temporary harm to the eyes and skin. However, newer fixture
and compliance with guidelines can make UVGI use safe and effective.
Whenever UVGI is used, precautions should be taken to alert and protect
clients. Staff should also receive appropriate education. Warning signs in
languages should be posted on fixtures and wherever UVGI is used. For
HIGH INTENSITY ULTRAVIOLET ENERGY
PROTECT EYES AND SKIN
Wherever UVGI is used, a routine maintenance program should be implemented
ensure that lamps are checked and replaced regularly.
Lamps should be replaced once a year or as directed by the manufacturer.
Francis J. Curry National Tuberculosis Center
WAC 246-324-190 Provisions for patients
with tuberculosis. A licensee providing inpatient services for patients
with suspected or known infectious tuberculosis shall:
(1) Design patient rooms with:
(a) Ventilation to maintain a negative pressure condition in each
patient room relative to adjacent spaces, except bath and toilet areas,
(i) Air movement or exhaust from the patient room to the out-of-doors
with the exhaust grille located over the head of the bed;
(ii) Exhaust at the rate of six air changes per hour; and
(iii) Make-up or supply air from adjacent ventilated spaces for four or
less air changes per hour, and tempered outside air for two or more air
changes per hour;
(iv) Ultraviolet generator irradiation as follows:
(A) Use of ultraviolet fluorescent fixtures with lamps emitting wave
length of 253.7 nanometers;
(B) The average reflected irradiance less than 0.2 microwatts per
square centimeter in the room at the five foot level;
(C) Wall-mount type of fixture installed over the head of the bed, as
close to the ceiling as possible to irradiate the area of the exhaust grille
and the ceiling; and
(D) Lamps changed as recommended by the manufacturer; and
(b) An adjoining bathroom and toilet room with bedpan washer; and
(2) Provide discharge information to the health department of the
patient's county of residence.
[Statutory Authority: Chapter
71.12 RCW and RCW 43.60.040.
95-22-013, § 246-324-190, filed 10/20/95, effective 11/20/95.]
Washington Administrative Code
As of April 2, 2003