There were several TB outbreaks in health-care facilities in the late 1980s and early 1990s. In response, guidelines and regulations were developed and implemented to help ensure safe TB control practices. Investigations of these outbreaks found lapses in administrative, engineering, and respiratory protection control measures. Even though engineering controls are secondary to administrative controls, they are still vital to a complete TB control program. Highlights from national guidelines are included below.

The most comprehensive TB control guideline for health-care facilities published to date is the CDC document, Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities, 1994, commonly referred to as the CDC Guidelines. This document includes Supplement 3: Engineering Controls, which contains recommended engineering controls for isolation rooms.

Much of this ICS isolation room guideline is based on the CDC Guidelines. Engineering control recommendations for the design of TB patient rooms include exhausting air to create negative pressure. For isolation room exhaust, the preferred practice is to directly exhaust to the outdoors. If recirculation is unavoidable, then high efficiency particulate air (HEPA) filters are recommended. A minimum ventilation rate of 12 air changes per hour (ACH) is recommended for isolation rooms that are being renovated or newly constructed, and where HEPA filter units are used to supplement the central system ventilation.

For existing isolation rooms, the CDC Guidelines are less restrictive. Increasing the isolation room air change rate to 12 ACH is recommended where feasible, but a minimum of 6 ACH is allowed. The guidelines include the caveat that 6 ACH is "based on comfort- and odor-control considerations" rather than infection control concerns. Higher ventilation rates "are likely to produce an incrementally greater reduction in the concentration of bacteria." In ICS’s experience, 12 ACH is usually feasible in existing isolation rooms.

The CDC Guidelines also include recommendations for testing and monitoring isolation rooms. The recommendations address testing methods and frequency of testing.

The AIA has published a guideline titled Guidelines for Design and Construction of Hospitals and Health Care Facilities. These guidelines apply to the design and construction of new health-care facilities and major renovations in existing facilities.

Recommendations of the 1996-1997 AIA guidelines include the following: 12 ACH in isolation rooms, negative pressure, and daily confirmation of negative pressure when a room is used for isolation.

This guideline also recommends that air from isolation rooms be either exhausted outdoors or HEPA-filtered before recirculation. A separation of 25 feet is recommended between exhaust from isolation rooms and other ventilation system intakes or occupied areas.

The Occupational Safety and Health Administration, U.S. Department of Labor (federal OSHA) is preparing a new Occupational TB Control Standard.

Meanwhile, a 1996 compliance directive is in place: CPL 2.106 Ð Enforcement Procedures and Scheduling Occupational Exposure to Tuberculosis. The directive is based on the CDC Guidelines, but does not address air change rates.

Employers are required to maintain and test negative pressure in isolation and treatment rooms used by individuals with suspected or confirmed infectious TB disease.

Appendix B contains highlights of the following California regulations and guidelines: Interim Tuberculosis Control Enforcement Guidelines, published and enforced by the California Division of Occupational Safety and Health (Cal/OSHA), and the California Mechanical Code (CMC), enforced by the Office of Statewide Health Planning and Development (OSHPD).