Cause of Device-Related Incident
Device factors; External factors

Clinical Specialty or Hospital Department
Clinical/Biomedical Engineering; Facilities Engineering

Device Factors
Improper maintenance, testing, repair, or lack or failure of incoming inspection

Document Type
User Experience Network (UEN) reports

External Factors
Medical gas and vacuum supplies

Mechanism of Injury or Death

Support System Failures
*Not stated

Tampering and/or Sabotage
*Not stated

User Errors
*Not stated

Filters, Gas [15-649]; Medical Gas and Vacuum Systems [18-046]; Smoke Evacuation Systems, Surgical [16-262]

Use of Filters on Medical Gas System Outlets and Vacuum System Inlets

User Experience Network™ [Health Devices Dec 1994;23(12):494-5]


For several years, we have been using filters on our medical gas system outlets to trap dirt, bacteria, and water conveyed by the systems. We have also been using filters on our medical vacuum system inlets to prevent fluids, condensate, and smoke from contaminating the system. Are these uses of filters appropriate? Also, is it appropriate to use our vacuum system for smoke evacuation?


We have received many such questions and have seen filters used in these ways. However, we do see some problems with these practices, as discussed below. We further address the issue of smoke evacuation below in"Evaluation Update."

Medical gas system outlets

When used on medical gas system outlets to reduce contamination, the use of filters is only a temporary solution to a significant problem and is appropriate only if the underlying cause of the contamination will be corrected as soon as possible. Depending on their construction, filters can be used temporarily to prevent contaminants such as particles, bacteria, and liquid water from entering and harming attached medical devices and patients. However, filters will not remove water vapor and other gases, which can damage devices or injure patients, and can themselves become loaded with trapped contaminants. Like medical gas systems, filters require routine inspection and preventive maintenance; if contaminants are discovered, filters should be used only until the contamination problem is corrected and the pipeline cleaned.

Although filters can effectively trap dirt (e.g., oxide particles from improper brazing of the pipeline) until it can be blown from the system at a convenient time, in many cases, contamination will only get worse. For example, water found in medical compressed air is caused by failure of the production system and can allow bacteria and molds to colonize the pipeline; the longer repairs are delayed, the dirtier the system will become—and the more expensive the cleanup will be.

Not correcting the cause of any medical gas system contamination can place the hospital in violation of state and local building and health codes and Food and Drug Administration (FDA) drug regulations, as well as create a health and fire risk. The National Fire Protection Association's (NFPA) Standard for Health Care Facilities (NFPA 99-1993) dictates cleanliness requirements for medical gas pipelines and forms the basis for most state and local building codes governing healthcare facilities. Because any gas administered to a patient is considered a drug, FDA requirements on allowable contaminants also apply. For more information, see our Guidance Article and IPM Procedure on medical gas and vacuum systems in Health Devices 23(1-2), January-February 1994.

Medical vacuum system inlets

Vacuum systems, which are considered to be contaminated in the same manner as soil or sewage pipelines, do not need inlet filters. The suction canisters used when suctioning body fluids during surgical procedures have overflow valves and/or filters to prevent most materials from being inadvertently drawn into the vacuum system.

However, inlets that are frequently used or that are worn can become fouled by fluid overflow and dust; therefore, they must be routinely inspected and maintained (just as a filter would need to be if used) to maintain adequate flow and vacuum (i.e., greater than or equal to 85 L/min [3 SCFM] at greater than or equal to 305 mm [greater than or equal to 12 inches] Hg). Dirty vacuum inlets can be inexpensively cleaned by drawing a solution of hot water and detergent into them; the solution is typically trapped in and evaporated from the vacuum receiver. If the system is designed so that flow does not go through the receiver, commercially available solutions, specially designed to be vacuum-pump safe, can be used.

Filters are sometimes used on the inlet when the vacuum system is used for smoke evacuation. However, in many cases, vacuum systems do not provide adequate flow for this use, and filters can also restrict flow, further reducing the ability of the vacuum system to capture smoke effectively. In addition, most particles and condensates in surgical smoke are deposited in the vacuum hoses and suction canisters normally attached to the vacuum inlet, making a filter a redundant expense. (See "Evaluation Update" below for further discussion of smoke evacuation.)


  1. Routinely inspect and maintain medical gas and vacuum systems. Schedules and procedures are described in our IPM Procedure in Health Devices 23(1-2), January-February 1994, and in NFPA 99-1993, Standard for Health Care Facilities.
  2. Use filters on medical gas outlets only as a temporary measure to protect patients and devices against particles, bacteria, or liquid water found in the system. Develop a schedule of filter inspection and replacement and a plan to correct the source of contamination in a medical gas system as soon as possible. Note that filters will not remove water vapor or other gases, which can damage some medical devices. Water found in the system is a serious problem requiring immediate action to eliminate its cause and limit the extent and impact of the contamination.
  3. Use suction canisters for any suctioning procedure. Filters on vacuum inlets are not needed.
  4. Use smoke evacuators instead of the central vacuum system for smoke evacuation during most procedures.

Evaluation Update

General-Purpose Surgical Laser Smoke Evacuation Systems

In our Evaluation of smoke evacuators in Health Devices 19(1), January 1990, we noted that "particulate matter in the [surgical] smoke can deteriorate hospital vacuum systems." However, based on conversations with pump manufacturers and the fact that most particles will be trapped before entering the pipeline, we no longer believe that smoke poses a significant problem to the vacuum system. Even if a residue buildup does occur in the pipeline, it can be removed by routine flushing of the vacuum system with water and detergent.

Thus, the medical vacuum system can be used for smoke evacuation (without a filter) during procedures for which it provides sufficient flow. However, smoke evacuators should be used for most applications, which require higher flows.


  • Filters, Gas [15-649]
  • Medical Gas and Vacuum Systems [18-046]
  • Smoke Evacuation Systems, Surgical [16-262]

Cause of Device-Related Incident

Device factor: Improper maintenance, testing, repair, or lack or failure of incoming inspection

External factor: Medical gas and vacuum supplies

Mechanism of Injury or Death


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