Role of Engineering Controls in Compliance Requirements

Role of Engineering Controls in Compliance Requirements

By Homa Christensen

"Life is short, and the art long; the occasion fleeting; experience fallacious, and judgment difficult. The physician must not only be prepared to do what is right himself, but also to make the patient, the attendants, and externals cooperate." Thus, Hippocrates, the father of modern medicine, epitomized the art of the physician. "To do what is right" in terms of infection control and prevention has far-reaching implications, not only for physician, but for "the patient, the attendants, and externals." In keeping with World Health Organization's (WHO) World TB Day 2001, this article focuses on infection control and prevention of tuberculosis (TB) in healthcare facilities.

Infection Control and Prevention

The fundamental focus of any infection control program should be effective identification of potential infections risks, thorough determination of methods of transmission, and effectual prevention methods. Hospitals, by their very nature, present many potential hazards requiring constant vigilance to maintain a safe and healthful environment.1 An effective infection control program requires early detection, isolation, and treatment of persons with infectious disease.2

TB Control and Prevention

For centuries, TB has been responsible for the death of millions of people throughout the world. It has caused more deaths than any other infectious disease.3 TB is a disease caused by bacteria called Mycobacterium tuberculosis (M. tb.). Presently, disease caused by M. tb. is the leading cause of mortality among adults in the world4. Some 2 billion people worldwide--one in every three--are infected with M.tb. TB has re-emerged as a serious public health problem aggravated by proliferation of multi-drug resistant TB strains and nosocomial (hospital-acquired) infections; 15 million are infected in the U.S. alone5. Outbreaks of TB are largely attributed to weaknesses in TB control programs such as inadequate ventilation. Healthcare professionals are at a greater risk of infection due to the constant exposure in the work environment. A recent study links the tuberculin conversion among healthcare workers to inadequate ventilation in patient rooms.6

TB is a preventable disease. Healthcare facilities caring for high-risk populations can take precautions to prevent its spread. Adequate ventilation is an important measure to prevent transmission of TB. Examples of preventive techniques include use of negative pressure rooms, HEPA filtration, ultraviolet germicidal light (to sterilize the air), and special respirators to filter out the droplet nuclei. One of the great medical advances in the 20th century is the treatment of TB. However, experience indicates that when inadequate attention is given to basic approaches, the probability of tuberculosis transmission is increased. The tenet of these basic approaches is prevention of the spread of infectious droplet nuclei into the general air circulation and reduction of their number in contaminated air.

Engineering Controls

Engineering controls are designed to reduce the concentration of infectious droplet nuclei in the air, prevent their dissemination, and render them non-infectious by killing the tubercle bacilli they contain. In the fight to prevent spread of TB, basic physical measures such as engineering controls will reduce microbial contamination of the air to minimize risk of exposure. Centers for Disease Control and Prevention (CDC) recommends the following engineering controls to reduce microbial contamination of the air:

  • local exhaust ventilation, i.e., source control,
  • General ventilation
  • Air cleaning7.

Engineering controls are based primarily on the use of adequate ventilation system supplemented with high efficiency particulate air (HEPA) filtration and ultraviolet germicidal irradiation (UVGI).

Compliance Requirements

Healthcare facilities must comply with a multitude of regulations and guidelines. Table 1 highlights a summary of rules and recommendations on negative pressure TB isolation rooms.


OSHA estimates that more than 5 million US workers are exposed to TB in the course of their work. OSHA inspectors use procedures outlined in Enforcement Procedures and Scheduling for Occupational Exposure to Tuberculosis. Citations will be issued to employers who have not provided appropriate protection to their employees. An OSHA citation will be accompanied by a list of feasible technologies such as engineering controls to abate conditions cited. An example of a feasible technology is a negative pressure TB isolation room, where room air is exhausted directly outside.

In 1994, OSHA published the Occupational Exposure to Tuberculosis Proposed Rule, which was released for public comment in October 1997. OSHA's intent to make it a final rule in April 2001 was published in Federal Register as part of the regulatory plan of the U.S. Department of Labor. The need for this rule has been hotly debated. For example, the Association for Professionals in Infection Control and Epidemiology (APIC) strongly advocates against this rule, stressing sufficiency of the 1994 CDC guidelines as adequate for protecting healthcare workers from exposure to TB.


It is of interest to note that the 1994 CDC Guideline is the central tenet to the regulations and guidelines listed in Table 1. In response to the increase in nosocomial outbreaks of TB in the late 1980s and early 1990s, CDC developed an extensive set of recommendations for the control of TB in healthcare settings, Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Healthcare Facilities. The guidelines recommend a TB control plan comprised of three hierarchical control measures.

  • Administrative--protocols for identifying, evaluating, and treating patients who may have TB
  • Engineering--general and local exhaust ventilation, HEPA filtration, and UVGI
  • Personal respiratory protection.


The Joint Commission on Accreditation of Healthcare Organizations (JCAHO), an independent and non-profit accrediting body, evaluates and accredits healthcare organizations and programs in the U.S. A predominant standards-setting body, JCAHO has published extensive standards with the intent of improving quality of healthcare. For example, JCAHO's Standard EC. 1.2, requires incorporation of the AIA 1996-97 Guidelines in planning for the size, configuration, and equipping the space of renovated, altered, or new construction.8


ASHRAE published the HVAC Applications Handbook in 1995. Chapter 7 of this document, "Health Care Facilities," recommends that infectious isolation rooms in new and remodeled facilities accommodate at least 6 air changes per hour.


AIA guidelines and updated recommendations are written to conform to the most current CDC's "Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health Care Facilities" and "Guidelines for Prevention of Nosocomial Pneumonia, 1994." Specific engineering control measures are recommended in section 7.2.C, Airborne Infection Isolation Rooms. At least one airborne infection isolation room is required to be located within individual nursing units; the room perimeter walls, ceilings, and floors, including penetrations, shall be sealed tightly so that air does not infiltrate the environment from the outside or from other spaces; and the room shall have self-closing devices on all exit doors.9

Other Regulations

Other relevant organizations to issue standards, guidelines, and/or recommendations include state health agencies and Francis J. Curry National Tuberculosis Center & California Department of Health Services. Statewide regulations usually are equal and/or more strict than regulations and guidelines set at the federal level. In California, for example, negative pressure isolation rooms are mandated by the 1995 California Mechanical Code (Title 24, Part 4, Ch. 4: Ventilation Air Supply) and California Division of OSHA (Cal/OSHA), Interim Tuberculosis Control Enforcement Guidelines (revised 3-1-97, Policy and Procedure C-47)

In its effort to assist healthcare facilities in their assessment of engineering controls, Francis J. Curry National Tuberculosis Center & California Department of Health Services published a document, How You Can Assess Engineering Controls for Tuberculosis in Your Healthcare Facility.10 The document highlights role of HEPA filter units and UVGI engineering controls in control and prevention of TB in healthcare settings.

HEPA filter units remove essentially all particles in the size range of droplet nuclei. The self-contained units (portable, ceiling-, or wall-mounted) will provide cleaned air to dilute infectious particles and to remove airborne particles. Advantages of HEPA units include improved air quality; ease of installation, maintenance, services, and flexibility.

UVGI radiation has been shown to kill or inactivate M. tb. in air. Two types of UVGI are used in TB control: in-duct and upper room irradiation. In-Duct consists of use of UVGI lamps inside an air duct or air cleaner. An appropriately designed, installed, and maintained in-duct UVGI system should effectively disinfect most recirculated air and therefore significantly reduce the risk of TB exposure from recirculated air. For TB control purposes, such a system would be almost equivalent to a 100% outside air system (ideal for high-risk settings), which is very expensive to install & operate. Upper-Room consists of use of mounted UVGI lamps in a room where there is a risk of TB spreading. Advantages of UVGI include its use as an upgrade to an existing system and its ability to remove most infectious particles from air without significant reduction to the airflow.


Various studies and TB outbreak investigations have shown that lack of early identification and appropriate control measures (e.g., lack of negative pressure in isolation rooms and performance of high-hazard procedures under uncontrolled conditions) resulted in the exposure and subsequent infection of various hospital employees.

An effectual infection control program is "To do what is right." As such, it is an imperative in the highly regulated environment of healthcare settings. The implications of compliance with various rules, regulations, guidelines, and recommendations should be carefully evaluated. More importantly, the altruistic motive to equally protect patients, healthcare workers and others brings the need for effective infection control programs to the forefront at any healthcare facility.

For a complete list of references visit:

Homa Christensen is a Market Analyst at Veloz Holdings, Inc. She received a Bachelor of Science degree and an MBA from California Polytechnic State University, San Luis Opispo.

Table 1.



Criteria Tb Standard 1OSHA Proposed CPL 2.106 2OSHA Directive 3CDC 4ASHRAE 5AIA
Room Designation Negative pressure TB Isolation and treatment Rooms TB Isolation and treatment Rooms Infectious isolation Room Infectious isolation Room
Facility Type New and remodeled New and remodeled New and remodeled New and remodeled New and remodeled
Total Air Changes Per Hour (ACH) At Least 12 Prefer > 12 > 6 minimum >6 Prefer >12 Minimum > 6 6 >12
Total Ach includes HEPA Yes Yes, if used to achieve 12 ACH Yes, if used to achieve 12 ACH No Yes
Engineering Controls        
In-Room HEPA Recirculation Yes Yes, if used to achieve 12 ACH Yes, if used to achieve 12 ACH No Yes
HEPA-Filtered Recirculation To Other Areas Yes Only if unavoidable Only if unavoidable No Yes
Dedicated Exhaust Required No No No No No
UVGI Supplemental Yes, supplemental to ventilation Yes supplemental to ventilation Yes, supplemental  to ventilation Not addressed Yes, supplemental to ventilation
Monitoring of Negative Pressure Yes Daily check while used for isolation Daily check while used for isolation Not addressed  
1 Occupational Safety and Health Administration (OSHA). Occupational Exposure to Tuberculosis; Proposed Rule- 62:54159-54309.
2 OSHA Directives. CPL 2.106-Enforcement Procedures and Scheduling for Occupational Exposure to Tuberculosis
3 Centers for Disease Control and Prevention (CDC). Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities. 1994. MMWR 1994; 43 (No. RR-13).
4 American Society of Heating, Refrigerating , and Air Conditioning Engineers (ASHRAE). 1995 HVAC Applications Handbook, Chapter 7: Health Care Facilities.
5 American Institute of Architects (AIA). 1996-1997 Guidelines for Design and Construction of Hospital and Health Care Facilities. Published by The Academy of Architecture for Health with assistance from the Department of Health and Human Services (DHHS).
Source (excluding 1): Francis J. Curry National Tuberculosis Center

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