QuantiFit 2 Fit Tester Detects Leak in Respirators Passed by CNC Technology | Air-Met Scientific

QuantiFit 2 Fit Tester Detects Leak in Respirators Passed by CNC Technology

Respirators are an effective way to prevent hazardous contaminants such as dust, fumes and chemicals from entering a person’s body. Respirator fit test determines whether a specific make, model and size of the respirator achieves an adequate seal on an individual’s face and therefore provides workers with the highest level of protection achievable.

There are several accepted and validated fit test methodologies. These are either qualitative fit test or quantitative respirator fit test and each with their own benefits and limitations. Qualitative methodologies such as the Aerosol Taste Test (ATT) rely entirely on the subject’s honesty and ability to detect the taste solution. Quantitative methodologies such as Ambient Aerosol Condensation Nuclei-Counting (CNC) also present limitations in which will be discussed below.

Controlled Negative Pressure (CNP), an RESP-FIT approved negative pressure respirator fit test methodology present many benefits over CNC and has only one limitation – it cannot currently fit test N95 disposable masks. That is really it!

Unless you are fit testing disposables, there are more benefits to using CNP technology than CNC technology. With fit testers such as the OHD QuantiFit 2, you can:

• Fit test anywhere – without the need for a controlled environment, fit testing with the QuantiFit 2 allows users to perform tests in any environment: inside, outside, dirty environments or clean. As long as air is present, a fit test can be performed.
• No ongoing consumable costs – unlike older technologies that require a range of consumables such as wicks and alcohol solutions, the QuantiFit 2 only requires air for testing.
• No alcohol wick to warm up – the whole test can be performed in as little as 2 minutes
• No need to wait 30 minutes after consuming food or having a smoke
• No waiting five minutes to equalise the subject and machine prior to testing
• Multiple donnings – CNP is the only fit testing technology that uses multiple donnings within the fit test protocol therefore ensuring users know how to consistently don the respirator correctly. This is made even easier by the QuantiFit2 with the step-by-step instructions on the colour touch screen display.

The OHD Fit Testing Product Range

Case Study: NSW Police Masks Passed by CNC Technology Yet Failed By CNP Technology

NSW Police members are issued multiple masks due to the nature of work they are required to attend to so accuracy and speed of the fit testing program is vital. That is until Air-Met Scientific was invited to demonstrate the QuantiFit 2 Fit Tester!

The Senior Sargent attended the trial equipped with the three masks that he had been issued and had all passed using CNC instrumentation. Two of these masks are used by emergency responders and our armed forces and can be difficult to test using the CNC method. The difficultly with this style of long duration worn face mask is how to probe the mask so the test can be completed, and as you test each subject with their own issued mask it can be very time consuming.

With the QuantiFit 2, it as simple as screwing on the adapter kit and pressing go. The test is over in under 2 minutes.

After explaining the fit test procedure with the Senior Sargent, we commenced testing on all three of his masks with the QuantiFit 2. The results were not as we had hoped for considering only 2 weeks earlier they had all passed using CNC technology. Two of his three masks that we tested had surprisingly failed and we couldn’t understand why.

To try to understand what had happened, we first looked at the donning procedure and could find no fault in the way he was donning the mask, so we moved on to seeing if the mask had a leak. To test if the mask had a leak, a negative test was conducted by donning the mask and blocking the inhalation valve, then drawing a deep breath in and looking for a leak. Both masks passed the manual procedure.

We then decided to check this result with the OHD QuantiCheck. The QuantiCheck is the first quantitative user seal check device. The user engages the QuantiCheck, takes a comfortable breath and holds. At the lowest point of the negative pull, the system starts a calculation, which is an OHD proprietary algorithm, that measures pressure loss from the respirator. The system simply indicates that the weakest point will be the required air entry point into the mask. The system is a static user seal check indicating the fit of the mask at the point in time the system is used. A quantitative check of respirator fit can be performed by the user each time the mask is donned. The QuantiCheck also passed for both masks.

It was confusing. How could a respirator pass using CNC technology and a negative pressure check yet fail using CNP technology? It should have passed.

Our final option was to have the failed masks bench tested. A bench test is used to check the integrity of a mask’s seal and looks for a fault within the mask itself. The results of the bench test proved that it was the mask that had an integrity failure and not the testing procedure using the QuantiFit 2. Of the two failed masks, the first mask had a blade of grass in the drinking tube and the second had a leak on a failed seal.

Once it was established that it was the masks and not the testing procedure that had failed, both masks were serviced and a new trial was undertaken. Both masks passed with a result of over 2000 after re-testing.

Respirator Fit Testing with Controlled Negative Pressure looks for the Smallest Leaks 

Results from the trial with the NSW Police showed that the pass we saw with the negative pressure respirator fit test was due to the high pressure we were drawing against the mask, yet as the mask only had a very small leak, it was therefore not detectable. CNP looks for the smallest leak. The masks were only failing by the tiniest of margins (443/500 and 473/500) and this was not detectable by the CNC instrumentation as they are using particles to perform the test, not air. CNP is the only technology that can highlight a faulty mask at the fit testing stage that might otherwise put you and your team at risk.