Compressed Air Safety and Quality in Healthcare

image showing pipeline of gases vacuum adaptor on wall for helping patient in operating room.

Moisture measurement: A key indicator for medical compressed air systems

Traditionally, compressed air has been called the fourth utility in industry – after electricity, gas and water.  The same is true in the healthcare sector, where compressed air is an essential utility for a wide range of both general and specialized hospital duties. 

Compressed air equipment has been used widely and without major problems in healthcare applications for many years.  Recently, however, the need to comply with increasingly stringent quality and safety standards, combined with the ever-present risk of legal action and compensation claims, has led to growing concerns about the perceived dangers associated with moisture in compressed air systems. 

Moisture in compressed air

Two key issues are traceability and compliance, required both to ensure patient safety and provide evidence in the event of an issue arising. 

Unlike other medical gases, such as nitrous oxide and Entonox, where there are rigidly controlled and fully traceable chains of custody via external suppliers, compressed air is generated on site and distributed widely throughout each facility.  This makes its safe and efficient operation totally dependent on the quality of the initial installation, the reliable operation of compressors, dryers and ancillary devices, the accuracy and dependability of monitoring and control systems, and the standard of maintenance and repair. 

Moisture is an inherent problem within compressed air systems, as naturally occurring water vapor is drawn into the compressor intake, from where it travels downstream in gaseous form or condenses to a liquid in pipework or other system components.  Additionally, moisture can enter the system through damaged pipework, leaking components or during routine maintenance. 

Regardless of its source, moisture within a compressed air system will cause problems.  These include: 

Corrosion of metal surfaces, which in extreme circumstances can either break away as small particles, potentially entering the downstream compressed air feed, or lead to component failure. 

Reduction in system efficiency, where moisture mixes with compressor lubricants to form a compound that can cause moving parts to stick or move erratic.

Microbial growth, which is potentially the greatest risk for compressed air systems used in healthcare applications, as bacteria and fungi spores can contaminate downstream air equipment. 

The implications of contaminated compressed air are clear and are of concern.

Measuring moisture content in medical systems 

Moisture is normally removed using a combination of filters/separators to capture aerosols and drain condensed water, plus either refrigerant or desiccant dryers to eliminate, or at least reduce to a safe and mandated level, the presence of water vapor. 

If all these systems are functioning efficiently, the compressed air delivered to the point of use will be to the standard required – normally HTM O2 – and will be safe to use.  However, risks arise if a system malfunctions or moves outside its correct operating parameters.  This is especially true of desiccant dryers, where the operational margins can be slim.  It only requires a minor increase in water content for a desiccant column adsorbing water vapor efficiently to suddenly become saturated and in need of regeneration, with the risk of excess moisture being carried downstream. 

The solution is to fit moisture or dew-point sensors.  These do, however, need to be capable of producing consistent and precise measurements down to extremely low levels of water vapor contamination if they are to comply with current guidelines.   For example, the European Pharmacopeia recommends that the maximum allowable moisture concentration in medical gases is 67 ppm (parts per million) by volume, which is equivalent to -46 ^°C dew point at atmospheric pressure.  The UK HTM 02 guidelines adopt the same criteria and also state that ‘the dryer control system should include a dew-point hygrometer and display with a minimum accuracy of ±3 ^°C in a range from -20 ^°C to -60 ^°C atmospheric dew point, with a set point of -46 ^°C.

These rigorous criteria demand the use of robust and extremely accurate dew-point sensors, capable of producing consistent and repeatable measurements with minimal drift over time.  Devices such as our Easidew EA2 Dew-Point Transmitter and Easidew 34 Transmitter are therefore ideal for this application, with stable ceramic metal-oxide sensor technology providing a measuring range from -110 to +20 ^°Cdp and an accuracy of ±2 ^°Cdp. 

Fitting Easidew EA2 transmitters to dryer outlets as part of a real-time monitoring and control system, with appropriate alarm outputs and traceability recording processes, provides the precision, dependability and peace of mind that healthcare professionals require to ensure that the potential problems of moisture contamination in compressed air are eliminated. 

Learn more about our compressed air solutions. 

To discuss your requirements, please contact our team today.  

Did you know ?

Health Technical Memorandums (HTMs) have been widely used in the UK healthcare sector for many years.  They have been written to complement broader industry and international standards and are intended to provide guidance and technical requirements for the design, installation and operation of specialized building and engineering systems used in the delivery of healthcare.  The ultimate goal is to define best practice and ensure the safe and efficient operation of healthcare facilities. 

At present, there are nine categories, each subdivided into different sections, covering topics as diverse as ventilation systems, decontamination and water equipment, electrical installations and the disposal of healthcare waste. 

To learn more, visit NHS England. 