Medical environments are a place where Volatile Organic Compounds (VOCs) need to be monitored, whether it be to meet regulations such as the Human Fertilisation and Embryology (HFEA) regulations for air quality in tissue laboratories, or ensuring that harmful gases used to sterilize tools and equipment used in hospitals has been removed to permitted levels

A common gas for sterilization of equipment destined for medical usage is Ethylene Oxide (EtO) Ethylene Oxide has an EH40 time-weighted average of 1 part per million (PPM) and is capable of causing cancer and/or heritable genetic damage and also can be absorbed through the skin for which there are concerns that dermal absorption will lead to systemic toxicity.^[1]

For many medical devices, sterilization with ethylene oxide may be the only method that effectively sterilizes and does not damage the device during the sterilization process. Medical devices made from certain polymers (plastic or resin), metals, or glass, or that have multiple layers of packaging or hard-to-reach places (for example, catheters) are likely to be sterilized with ethylene oxide.^[2] About fifty percent of all sterile medical devices in the U.S. are sterilized with ethylene oxide. The types of devices that are sterilized with ethylene oxide range from devices used in general health care practices such as wound dressings to more specialized devices used to treat specific areas of the body e.g. stents.^[2]

For ethylene oxide sterilization, two voluntary consensus standards exist, these are ANSI AAMI ISO 11135:2014 and ANSI AAMI ISO 10993-7:2008(R)2012. These standards describe how to develop, validate, and control ethylene oxide sterilization processes for medical devices and the acceptable levels of residual left on a device after it has undergone sterilization. These standards help ensure levels of ethylene oxide on medical devices are within safe limits since long-term and occupational exposure to ethylene oxide has been linked to cancer.^[2]

What are the Benefits of Ethylene Oxide Processing?
Materials sterilized with EO are not exposed to excessive heat, moisture, or radiation so a wide variety of materials, such as polymeric components commonly used in medical devices, can be sterilized with EtO. Material compatibility is described in AAMI TIR 17. Products can be sterilized in their final packaging since EtO will permeate the sealed films and cartons used to package the device ensuring total sterilization.^[3]

Monitoring Ethylene Oxide
One of the simplest and effective ways to measure VOCs is Photoionisation detection (PID), due to its speed of response and wide range. This application is a process control application, monitoring the EtO depletion throughout the process. In normal industrial hygiene and the measuring of workplace exposure limits, fixed PID detection is not suitable for the monitoring of Ethylene Oxide, at low levels. In the monitoring of Ethylene oxide in the sterilization process, the gas is contained in a sterilization booth and vented, a fixed solution is well suited to this application.

ION Science offers a range of solutions for VOC detection, and the Falco fixed detector provides a unique feature set and includes a user-friendly interface, plus an easy-fit maintenance and service design. The internal MiniPID is easily accessible so no need for hot work permits to perform maintenance. The Falco has four detection ranges available, 0–10ppm, 0–50ppm, 0–1,000ppm, and 0–3,000ppm, suitable for any level of monitoring.

References

1. EH40/2005 Workplace exposure limits (fourth edition 2020)
2. https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/ethylene-oxide-sterilization-medical-devices (Obtained 22/06/21)
3. https://www.steris-ast.com/services/ethylene-oxide-sterilization/ (Obtained 22/06/21)

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