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The advantages of CNP when fit testing

12 June 2020

With fit testing and RPE such a hot topic currently, a growing number of RPE wearers are now switching to reusable, half- or full-mask models. Reasons for this decision include leaving more disposable products free as resources for key workers, as well as being a more sustainable and environmentally friendly solution.

Long-established in the USA, controlled negative pressure (CNP) technology is now fast becoming a preferred method of fit testing in the UK because it is ideal for half- and full-mask testing and is referenced in the HSE INDG479 guidance on RPE fit testing. 

OHD, a leading manufacturer of CNP technology, has been supplying Quantifit to government agencies, emergency responders and industry across the USA for decades. And, in partnership with Shawcity in the UK, the Quantifit has also been supplied to the Fire Service, Utilities and other industry. 

Traditional ambient air particle counting methods only work where there is particulate present in the air. However, commonly there is not enough present, so it has to be artificially introduced using consumables such as salt tablets and a particle generator to create a ‘salt fog’. This has been the standard approach to quantitative fit testing in the UK for some years.

The main disadvantages of this type of technology are that it has a limited range of particle sizes which it can measure, and the ambient sampling range does not equate to the human respirable range. Particles also move in the air within a mask and can be subject to drift or streamlining. The placement of a probe or the location of a leak can all impact what the test will pick up. 

Ambient aerosol counting also requires specific environmental conditions which restricts where the tests can physically take place. Additionally, it means that the system is prone to particle contamination in areas such as the tubing, which result in higher levels of ongoing disruption, maintenance issues, manufacturer returns as well as additional cost of ownership implications.

What makes Quantifit different?
The technology behind Quantifit is clean and efficient. In simple terms, it uses air as the challenge agent and directly measures leaks, demonstrating that if air can get inside the mask, by definition, contaminants including vapours and gases potentially can too.

Using state-of-the-art controlled negative pressure, Quantifit establishes and maintains a slight vacuum inside the mask. To keep the pressure constant, it must pull out any additional air that leaks into the respirator. This precise cc/min measurement tells you how much air has leaked into the respirator, and this is converted into a fit factor.

The benefits Quantifit offers over traditional air particle counting methods are numerous and it offers truly portable fit testing. 

  1. No consumables: The Quantifit uses air as the challenge agent, and therefore does not require particles to be generated. This limits the amount of equipment the Quantifit requires and minimises the ongoing costs of fit testing
  2. Fit test even in outdoor, open environments: This allows for better air flow and less cross-contamination between individuals. It also ensures less close personal contact and makes 2m distancing easier to maintain. Being outdoors also reduces the risk of surface contamination
  3. Set up and use: Quantifit is ready to use after a one-minute daily calibration, so it is very time-efficient. With no consumables, it needs only air and a power source to operate
  4. Easy Clean Adaptors: Disinfect adaptors with wipes or solution between tests
  5. Eliminates condensation in tubing: Time-efficiency is improved with no tube cleaning or changing.

If you would like to find out why UK government organisations, the emergency services, utility companies and many more businesses have already chosen to switch to Quantifit, contact the team at Shawcity to discuss your requirements. 

As the exclusive supplier of Quantifit in the UK and Ireland, Shawcity can arrange demonstrations and training sessions with options to purchase, hire or ‘try before you buy’. A trade-in scheme is also available for those looking to invest in their own units and all contact-free deliveries and collections are free of charge.

01367 899419