North American Sterilization & Packaging Company
17 Park Drive, Franklin, New Jersey 07416 USA
Phone:1.973.209.4388    1.800.392.6310       Fax:1.973.209.6374        Email: info@naspco.com

(continued from Page 3, Load Configuration)

Speeding EtO-Sterilized Products to Market with Parametric Release (continued)

Sampling the Gases

To measure the headspace gases for parametric release precisely, a system must first be configured to draw representative samples of the process gases.

Sampling points must be selected wherever it is determined that a gas sample representative of process conditions can be obtained and carried to the analyzer. Unless the analyzer is of the type that can be directly connected to the vessel (bolted in-line with the recirculation blower), or equipped with remote sensors (such as fiber optics) that can be placed inside a vessel, then sampling lines (such as 0.25-in. stainless-steel tubing) must be installed to connect the vessel to the analyzer.

These lines should be kept as short as possible and must maintain a high enough temperature that the process gases will not condense before reaching the analyzer. Maintaining this temperature, or heat tracing, actually means keeping the sample gases at a higher temperature than that of the process gases to prevent condensation.

Also, all connections must be perfectly soldered and periodically leak tested. Removable compression fittings offer an alternative to soldering, but using them may prevent the system from being approved by certain safety agencies for use in a 100% EtO sterilizer.

Depending on the technology used to perform the gas analysis, a pump may also be necessary to draw a sample from the vessel. This pump, along with all other components of the gas analysis system, must satisfy all applicable electrical safety standards for use with vessels containing flammable gas mixtures. If the analyzer is to be placed within the sterilizer area, approval for such a position must be obtained by the appropriate institutions (such as insurance companies, building inspectors, and Underwriters Laboratories).

The sampling system, especially if it is functioning continuously, must return unused gases to the vessel. Sample pumps with a capacity of more than 1 L/min can alter the process conditions if they do not return exhaust to the vessel. In addition, such a closed system provides extra protection against inadvertent violations of emission standards and employee exposure.

There should be a calibrated temperature sensor next to each sample point. The closer the sensor is to the point, the more accurate the reading, especially in larger vessels. Process temperature monitoring systems that simply measure multiple points in the vessel and then average the readings to control chamber heating should not be used to control a gas analyzer.

Provisions should also be made to allow management to empirically determine whether stratification of the process gases is possible. Depending on the type of gas analyzer chosen, this can be accomplished by extending the sample port well into the interior of the vessel and then moving it about during a series of cycles so that samples are analyzed from the top, bottom, front, and rear of the vessel. Stratification can also be verified through the use of BI incubation data during fractional studies, or through the implementation of quantitative chemical indicators placed strategically throughout a load.⁹ If stratification is verified, then the selection of the sample point should be based on the location that has the lowest levels of process gas.

This website is designed for monitors with a resolution of 1024 x 768
and
to be viewed with MS Internet Explorer or Netscape Navigator Web Browsers

Send mail to fdpp@fdpp.com with questions or comments about this web site.
Copyright © 2001 North American Sterilization & Packaging Company, Inc.