Cause of Device-Related Incident
Device factors; Support system failures

Clinical Specialty or Hospital Department
Clinical/Biomedical Engineering; Infection Control; Nursing; Pulmonary / Respiratory Therapy

Device Factors
Design / labeling error; Improper maintenance, testing, repair, or lack or failure of incoming inspection

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Exposure to airborne infectious agents

Support System Failures
Poor prepurchase evaluation

Tampering and/or Sabotage
*Not stated

User Errors
*Not stated

Enclosures, Aerosol Treatment [18-048]

Full Enclosure Needed to Prevent Contamination during Pulmonary Procedures

Hazard [Health Devices Dec 1993;22(12):594-5]


Several types of aerosol treatment enclosures are intended to enclose patients and protect bystanders from contamination by infectious aerosols or toxic drugs during treatment of patients infected with tuberculosis (TB) or the human immunodeficiency virus (HIV). However, enclosures that do not provide full enclosure do not isolate the patient (see figure 1) and can be effective only if the patient's face is fully inside the cart. Unenclosed patients can easily move out of the airflow and contaminate the room air by coughing, which typically occurs during inhalation treatments for TB and HIV-related diseases (e.g., Pneumocystis carinii pneumonia).


During certain pulmonary procedures (e.g., sputum induction) and treatments (e.g., inhalation therapy), the patient is stimulated to cough. Coughing produces copious amounts of aerosols that, in patients with infectious TB, can infect others who inhale them. Patients who are HIV-positive or who have developed acquired immunodeficiency syndrome (AIDS) are becoming increasingly infected with multiple-drug-resistant tuberculosis (MDR TB) and often receive pentamidine isethionate to prevent or treat Pneumocystis carinii pneumonia. MDR TB is very difficult to treat and has a high mortality rate, and long-term exposure to pentamidine isethionate is potentially hazardous. Therefore, patients and healthcare workers must be protected from aerosol or drug exposures. Engineering controls that isolate the patient and trap the aerosols (see figures 2 and 3) can minimize the risk of infection and secondary exposure to drugs used during treatment.

The Centers for Disease Control and Prevention (CDC), in its Guidelines for Preventing the Transmission of Tuberculosis in Health-Care Settings, with Special Focus on HIV-Related Issues (1990), and the California Occupational Safety and Health Act (Cal OSHA), Section 5197 Occupational Tuberculosis Control, have established recommendations for dealing with TB and HIV patients in the healthcare setting. Ideally, healthcare facilities should isolate the patient within an enclosed space having airflow into the space and exhaust to the outdoors or, alternatively, high-efficiency particulate air (HEPA) filtration of recirculating air.

ECRI comment

ECRI interprets the CDC and Cal OSHA recommendations to mean that the patient must be completely prevented from contaminating others and be protected from being contaminated by other patients during treatment. Therefore, healthcare facilities should use a room or enclosed booth with an inward airflow (negative pressure) and exhaust to the outside (or at least use HEPA-filtered recirculation). Unlike many diseases, TB has the potential to spread rapidly through a population because it is transmitted by airborne particulates; intimate or close contact need not occur. At present, the only means of checking the spread of TB among healthcare workers (and patients) is to use 1) effective engineering controls for protecting everyone from potentially contaminated air and 2) respiratory protection where inadequate controls are in place. Engineering controls are also effective in minimizing worker exposure to hazardous drugs and are preferred over respirators, which are subject to user difficulties (e.g., lack of seal, discomfort, noncompliance). Enabling the patient to circumvent engineering controls (i.e., with the use of only partial enclosure) places healthcare workers and bystanders at great risk.

Manufacturers' action

Most aerosol treatment enclosure manufacturers can provide add-on drapes or canopies that will fully enclose the patient (see figures 2 and 3), and their instruction manuals will more clearly state the need to use full patient enclosures. They will also provide warning labels, describing proper patient isolation, to be placed on the enclosures.


  1. Use only enclosures that completely isolate the patient.
  2. If your enclosure does not fully isolate the patient, contact the manufacturer to obtain a full-isolation system, available from most aerosol treatment enclosure manufacturers.
  3. In the interim, if an enclosure must be used without full patient isolation, do the following:
    • Use the device only in areas that can effectively isolate the patient from the staff and other patients (e.g., a room with an inward airflow [negative pressure] and exhaust to the outside [or at least HEPA-filtered recirculation]).
    • Personnel attending the patient should wear fit-tested respiratory protection devices approved by the National Institute for Occupational Safety and Health (NIOSH) (so-called respirators, or HEPA masks, capable of filtering submicron particles from inspired air).
    • Instruct the patient to remain facing the filter with his or her head and body within the plane of the airflow opening.
    • Follow the manufacturer's instructions regarding filter maintenance to ensure that airflow over the patient is maintained.
  4. Before purchase, ensure that new enclosures fully and conveniently isolate the patient.


Enclosures, Aerosol Treatment [18-048]

Cause of Device-Related Incident

Device factors: Design/labeling error; Improper maintenance, testing, repair, or lack, or failure of incoming inspection

Support system failure: Poor prepurchase evaluation

Mechanism of Injury or Death

Exposure to airborne infectious agents

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