A Little Gas Goes a Long Way

Hospitals and other organizations around the world use single use ethylene oxide (EtO) cartridges for their sterilization. While these single use cartridges are without doubt much safer that the previous large cylinders there is still the risk of accidental rupture.

A ChemDAQ customer was performing a worst case scenario analysis and asked what the concentration of EtO from a 100g cartridge would be it is was released into an ventilated room of 5, cheap 000 cubic feet.

The calculation is fairly easy, calculate the amount of EtO in 100g (in moles), calculate the amount of air in the room, again in moles and find the ratio between the two, and scale to give the concentration in ppm. Click here for spreadsheet with details.

The answer is almost 400 ppm around the odor threshold; i.e. a little EtO goes a long way.  It is not a unique feature of EtO, but simply a reflection of the increase in volume of any liquid that converts to the gas or vapor form and similar calculations could be performed.

While these calculations are for worst case scenario planning, they do illustrate the need to be aware of the risks and to have a means to detect if there is leak (even if not 400 ppm), such as the ChemDAQ Steri-Trac continuous monitor for EtO. Sterilant gases such as EtO are essential for low temperature sterilization of medical devices and even though modern equipment is designed to very high standards problems may still occur.

With the appropriate engineering controls, continuous gas monitor, PPE, work practices and training, these sterilant chemicals can be used safely. ChemDAQ is pleased to do our part to help ensure the safe and continued use of chemical biocides such as EtO.