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Medical Devices

Hazards of Volume Ventilators and Heated Humidifiers


September 15, 1993


To: Hospital Administrators and Risk Managers:

This is to alert you that FDA has several reports of patient deaths and injuries resulting from malfunctioning volume ventilators and/or heated humidifiers, and to urge that you take certain precautions to prevent such incidents in the future.

One incident of fire, in which three patients died, is believed to have originated in either a Puritan-Bennett Cascade IA humidifier or in the Puritan-Bennett 7200 series ventilator to which the humidifier was attached. This incident is still being investigated. We have received reports that units from all series of Puritan-Bennett Cascade humidifiers and Puritan-Bennett ventilators have been associated with fires and/or overheating. We also have reports that humidifiers and volume ventilators from other firms have overheated.

In another incident, an employee sustained electrical injury requiring hospitalization when a Puritan-Bennett 7200 series ventilator chassis became electrically live as a result of a damaged power cord inside the unit.

To prevent further deaths and injuries, we recommend that you take the following precautions for all volume ventilators and heated humidifiers used in both health care facilities and homes:

  • Immediately remove from service any heated humidifier and/or volume ventilator which has shown signs of overheating, smoking or electrical malfunction (e.g., sparking or causing shocks). Do not return these units to service until they have been evaluated for safety by an authorized factory representative or other authorized personnel and repaired if necessary.
  • Use an audible temperature alarm that senses gas temperature in the line delivering gas to the patient on any humidifier used in conjunction with a volume ventilator. Be sure to test the alarm periodically for proper functioning.
  • Review the service and maintenance records for volume ventilators and heated humidifiers to assure that they currently meet all service recommendations of the manufacturer. (For example, Puritan-Bennett recommends replacing the thermoswitch in the Cascade I series humidifiers every five years.) Reviewing service records is especially important for used or remanufactured equipment.
  • Check power cords regularly for damage both inside and outside the unit.
  • Assure that power cords are properly fitted with strain relief devices inside the chassis.

If you have questions about this Notification, please contact FDA's  Division of of Small Manufacturers, International and Consumer Assistance (DSMICA) by e-mail at or by phone at 1-800-638-2041 or 301-796-7100

FDA Medical Device Public Health Notifications are available on the Internet. You can also be notified through email each time a new Public Health Notification is added to our web page. To subscribe, send an email request to

Please remember that the Safe Medical Devices Act of 1990 requires hospitals and other user facilities to report deaths, serious illnesses and injuries associated with the use of medical devices, including humidifiers and ventilators, to FDA or to the manufacturer. You may report such Incidents by phoning 301-427-7500, by FAXing 301-881-6670, or by writing FDA, CDRH, MDR User Reporting, P.O. Box 3002, Rockville, MD 20857.


Sincerely yours,

Bruce Burlington, M.D.
Center for Devices and Radiological Health
Food and Drug Administration


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