Water for Sterilizing Medical Devices
Water for sterilization — including steam sterilization and autoclaving — has an updated requirement and standard. This is for water used to feed steam sterilizers and autoclaves, and applies to sterilizing surgical tools and instruments.
New Standard
AAMI calls the new standard for water for sterilizing medical devices “Water for the Processing of Reusable Medical Devices”. This is technically AAMI ST108. The Association for the Advancement of Medical Instrumentation (AAMI) led this effort and instituted this new protocol. The Technical Information Report (TIR34) was published in 2014. Because steam sterilization is widely used in the processing of surgical instruments, ensuring that feed water meets these stricter criteria ensures reliable sterilant generation and protects equipment longevity.
Note: AAMI ST79 is the standard for the broader steam sterilization process.
Water Technologies
Water quality is an important consideration for all stages of medical device manufacturing and reprocessing. SnowPure Water Technologies provides components for several parts of these systems.
The new AAMI Standard (108) no longer allows a direct water feed to sterile processing.
Sterile Water Loop
In fact, a sterile water loop is now required. It must have a velocity of 3-5 feet per second (fps) being recirculated continuously through a UV (254 nm), with an endotoxin filter to ensure that the last water that touches surgical instruments is free of bacteria and endotoxins. This higher quality water protects equipment, lowers rates of infection, and improves patient outcomes.
An RO system followed by Electropure EDI is an ideal solution to feed the loop for meeting these new standards. SnowPure has an additional advantage with our “DER” EDI which removes endotoxins during the purification process. These are sanitary style EDI modules which are specifically designed to efficiently trap >95% of endotoxins when using SnowPure’s operational procedures.
Opportunities for SnowPure OEMs
This new standard provides an excellent opportunity for SnowPure OEMs to develop sterile water systems to target the large medical device market, as well as hospitals. Water system flows are generally in the 1 to 10 gpm (225 to 2,225 l/hr) range with the loop pump sized from 5 to 20 gpm (1.4 to 5.5 m3/hr), but may be larger.
Water must also have a low level of dissolved gases to make the steam. Per EN 285 (DIN 285), non condensable gases (NCG) must be less than 3.5% v/v in the condensate. This includes N2, O2, and CO2. To remove all dissolved gases, a vacuum-only membrane degasifier system should be used.
The 3.5% v/v NCG limit comes from experimental work by Bowie and Dick in the 1960s. Their experiments showed that:
- Small amounts of air mixed with steam can prevent steam penetration into porous materials
- Above a certain concentration, sterilization failures begin to appear
A schematic RO-GTM-DER or RO-GTM-EDI and loop system is shown below:
See article at https://www.aami.org/news/article/standards-spotlight-new-projects-for-sterilization-and-htm-education