How ISO 14644 Works: A Look at the Standard Guiding the Sterilization of Medical Equipment

Codified rules are important in the medical industry because of the harm that mistakes can bring about. Scientists have known since the late 1800s that bacteria can cause complications and even death in patients. For sterilization methods, the standard is ISO 14644. This standard lays out the guidelines for clean rooms, the methodology for proper sterilization and the techniques for measuring contamination.

Particle Filtration

Medical Instruments


Metal instruments can be sterilized after the fact, but plastic and food needs to be manufactured in a clean room environment. A favorite visual of viruses-gone-wrong sci-fi movies, the Hollywood clean room shows white-clad workers with white masks in a white room. What the movies do not show is the most important part of sterile rooms—the ventilation system.

Both the clothing that technicians wear and the HVAC system filter out particulates that are larger than .5 microns. To get an idea of the size of a half of a micron, the period at the end of this sentence is a little more than 600 microns, and a spider’s web is 3 microns thick. Anthrax is between 1-5 microns. Viruses are smaller than .5 microns, but viruses do not last long outside a human host.

Clean rooms use a constant-flow air-circulating system and a variety of sterilization techniques. Clean room water must be constantly monitored to ensure it is kept clean. According to Apple Rubber, this is done by measuring total organic carbon, resistivity and pyrogens.

After Production Sterilization

There are various methods for sterilizing products after they have been manufactured. The most common method of sterilization, according to the Centers for Disease Control and Prevention, is pressurized steam delivered at around 260 degrees Fahrenheit. Steam has high penetrability and easily gets into porous spaces and fabrics. One of the problems with steam disinfecting, however, is that it can be corrosive to some materials, especially medical implants that rely on their malleability.

Ethylene oxide is used for heat-sensitive and moisture-sensitive medical devices. Bacteriological agents cannot live in an ethylene oxide environment, so devices are exposed to this gas for an extended period of time. New alternatives to ethylene oxide are being developed, because its stabilizing agent is hydroflorocarbon, which is highly regulated.

Testing Methods

Most regulatory standards have a quality assurance component, and ISO 14644 is no exception. Sterile facilities have both mechanical and chemical indicators of contamination. Mechanical indicators, such as the Bowie-Dick test, either measure the size of airborne particulates or evaluate the effect of particles on the equipment like the HVAC vacuum pump.

Chemical indicators react to biological agents or their byproducts, giving off a color signature. Enzymes are used that attach at one end to specific structures of bacteria. The other end reacts with a color indicator, so the indicator changes color if the bacterium is present. Different contamination risks have varying requirements, but according to the University of Rochester Medical Center, most hospitals use mechanical indicators continually, and then use chemical indicators before introducing new products, after the sterilizer has been repaired or after a sterilization failure.


  1. Sterilization of Medical Equipment is a very common problem we face in hospitals of under developed countries. Mostly we create problems for our own people by not following the proper sterilization of surgical and medical equipment.