Role of Engineering Controls in Compliance Requirements

March 1, 2001

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; experiencefallacious, and judgment difficult. The physician must not only be prepared todo what is right himself, but also to make the patient, the attendants, andexternals cooperate." Thus, Hippocrates, the father of modern medicine,epitomized the art of the physician. "To do what is right" in terms ofinfection control and prevention has far-reaching implications, not only forphysician, but for "the patient, the attendants, and externals." Inkeeping with World Health Organization's (WHO) World TB Day 2001, this articlefocuses on infection control and prevention of tuberculosis (TB) in healthcarefacilities.

Infection Control and Prevention

The fundamental focus of any infection control program should be effectiveidentification of potential infections risks, thorough determination of methodsof transmission, and effectual prevention methods. Hospitals, by their verynature, present many potential hazards requiring constant vigilance to maintaina safe and healthful environment.1 An effective infection controlprogram requires early detection, isolation, and treatment of persons withinfectious disease.2

TB Control and Prevention

For centuries, TB has been responsible for the death of millions of peoplethroughout the world. It has caused more deaths than any other infectiousdisease.3 TB is a disease caused by bacteria called Mycobacteriumtuberculosis (M. tb.). Presently, disease caused by M. tb. is the leadingcause of mortality among adults in the world4. Some 2 billion peopleworldwide--one in every three--are infected with M.tb. TB has re-emerged as aserious public health problem aggravated by proliferation of multi-drugresistant TB strains and nosocomial (hospital-acquired) infections; 15 millionare infected in the U.S. alone5. Outbreaks of TB are largelyattributed to weaknesses in TB control programs such as inadequate ventilation.Healthcare professionals are at a greater risk of infection due to the constantexposure in the work environment. A recent study links the tuberculin conversionamong healthcare workers to inadequate ventilation in patient rooms.6

TB is a preventable disease. Healthcare facilities caring for high-riskpopulations can take precautions to prevent its spread. Adequate ventilation isan important measure to prevent transmission of TB. Examples of preventivetechniques include use of negative pressure rooms, HEPA filtration, ultravioletgermicidal light (to sterilize the air), and special respirators to filter outthe droplet nuclei. One of the great medical advances in the 20th century is thetreatment of TB. However, experience indicates that when inadequate attention isgiven to basic approaches, the probability of tuberculosis transmission isincreased. The tenet of these basic approaches is prevention of the spread ofinfectious droplet nuclei into the general air circulation and reduction oftheir number in contaminated air.

Engineering Controls

Engineering controls are designed to reduce the concentration of infectiousdroplet nuclei in the air, prevent their dissemination, and render themnon-infectious by killing the tubercle bacilli they contain. In the fight toprevent spread of TB, basic physical measures such as engineering controls willreduce microbial contamination of the air to minimize risk of exposure. Centersfor Disease Control and Prevention (CDC) recommends the following engineeringcontrols 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 ventilationsystem supplemented with high efficiency particulate air (HEPA) filtration andultraviolet germicidal irradiation (UVGI).

Compliance Requirements

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


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

In 1994, OSHA published the Occupational Exposure to Tuberculosis ProposedRule, which was released for public comment in October 1997. OSHA's intent tomake it a final rule in April 2001 was published in Federal Register as part ofthe regulatory plan of the U.S. Department of Labor. The need for this rule hasbeen hotly debated. For example, the Association for Professionals in InfectionControl and Epidemiology (APIC) strongly advocates against this rule, stressingsufficiency of the 1994 CDC guidelines as adequate for protecting healthcareworkers from exposure to TB.


It is of interest to note that the 1994 CDC Guideline is the central tenet tothe regulations and guidelines listed in Table 1. In response to the increase innosocomial outbreaks of TB in the late 1980s and early 1990s, CDC developed anextensive set of recommendations for the control of TB in healthcare settings, Guidelinesfor Preventing the Transmission of Mycobacterium Tuberculosis in HealthcareFacilities. The guidelines recommend a TB control plan comprised of threehierarchical 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), anindependent and non-profit accrediting body, evaluates and accredits healthcareorganizations and programs in the U.S. A predominant standards-setting body,JCAHO has published extensive standards with the intent of improving quality ofhealthcare. For example, JCAHO's Standard EC. 1.2, requires incorporation of theAIA 1996-97 Guidelines in planning for the size, configuration, and equippingthe space of renovated, altered, or new construction.8


ASHRAE published the HVAC Applications Handbook in 1995. Chapter 7 of thisdocument, "Health Care Facilities," recommends that infectiousisolation rooms in new and remodeled facilities accommodate at least 6 airchanges per hour.


AIA guidelines and updated recommendations are written to conform to the mostcurrent CDC's "Guidelines for Preventing the Transmission of MycobacteriumTuberculosis in Health Care Facilities" and "Guidelines for Preventionof Nosocomial Pneumonia, 1994." Specific engineering control measures arerecommended in section 7.2.C, Airborne Infection Isolation Rooms. At least oneairborne infection isolation room is required to be located within individualnursing units; the room perimeter walls, ceilings, and floors, includingpenetrations, shall be sealed tightly so that air does not infiltrate theenvironment from the outside or from other spaces; and the room shall haveself-closing devices on all exit doors.9

Other Regulations

Other relevant organizations to issue standards, guidelines, and/orrecommendations include state health agencies and Francis J. Curry NationalTuberculosis Center & California Department of Health Services. Statewideregulations usually are equal and/or more strict than regulations and guidelinesset at the federal level. In California, for example, negative pressureisolation 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 andProcedure C-47)

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

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

UVGI radiation has been shown to kill or inactivate M. tb. in air. Two typesof UVGI are used in TB control: in-duct and upper room irradiation. In-Ductconsists of use of UVGI lamps inside an air duct or air cleaner. Anappropriately designed, installed, and maintained in-duct UVGI system shouldeffectively disinfect most recirculated air and therefore significantly reducethe risk of TB exposure from recirculated air. For TB control purposes, such asystem would be almost equivalent to a 100% outside air system (ideal forhigh-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 riskof TB spreading. Advantages of UVGI include its use as an upgrade to an existingsystem and its ability to remove most infectious particles from air withoutsignificant reduction to the airflow.


Various studies and TB outbreak investigations have shown that lack of earlyidentification and appropriate control measures (e.g., lack of negativepressure in isolation rooms and performance of high-hazard procedures underuncontrolled conditions) resulted in the exposure and subsequent infection ofvarious hospital employees.

An effectual infection control program is "To do what is right." Assuch, it is an imperative in the highly regulated environment of healthcaresettings. 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 othersbrings the need for effective infection control programs to the forefront at anyhealthcare facility.

For a complete list of references visit:

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



CriteriaTb Standard1245
Room DesignationNegative pressureTB Isolation and treatment RoomsTB Isolation and treatment RoomsInfectious isolation RoomInfectious isolation Room
Facility TypeNew and remodeledNew and remodeledNew and remodeledNew and remodeledNew and remodeled
Total Air Changes Per Hour (ACH)At Least 12Prefer > 12 > 6 minimum >6Prefer >12 Minimum > 66>12
Total Ach includes HEPAYesYes, if used to achieve 12 ACHYes, if used to achieve 12 ACHNoYes
Engineering Controls    
In-Room HEPA RecirculationYesYes, if used to achieve 12 ACHYes, if used to achieve 12 ACHNoYes
HEPA-Filtered Recirculation To Other AreasYesOnly if unavoidableOnly if unavoidableNoYes
Dedicated Exhaust RequiredNoNoNoNoNo
UVGI SupplementalYes, supplemental to ventilationYes supplemental to ventilationYes, supplemental  to ventilationNot addressedYes, supplemental to ventilation
Monitoring of Negative PressureYesDaily check while used for isolationDaily check while used for isolationNot addressed 

For a complete list of references click here