The resistance to penetration by synthetic blood was tested for 10 filter material samples, and 10 full mask assemblies.
The test was conducted by clamping each sample, or full mask assembly, in a sample holding fixture. This fixture was mounted nominally 30 cm from the tip of a liquid-dispensing cannula. A pneumatic valve was used to deliver a horizontally projected stream of (2.00 ± 0.05) ml of synthetic blood to the target area around the centre of the sample, or full mask assembly, with a valve-open time of nominally 0.66 s. The inside surface of the sample was inspected for evidence of liquid penetration (from the outside surface) within nominally 10 s of delivery of the synthetic blood.
The filter materials were conditioned for a minimum of 4 hours in nominal conditions of 21 °C ambient temperature and 85% RH ambient relative humidity inside an environmental chamber. Tests were conducted on each sample and full mask assembly, within nominally 60 seconds of removal from the environmental chamber.
For the full mask assembly tests were performed by first removing the filter holder on the mask, then placing either a nominally 80 mm diameter filter cut from a larger sheet, or a pre-cut filter, within the holder and replacing the holder back on to the mask ensuring that the retaining clips on the holder are fully engaged onto the mask. Only masks with no face seals were used for the tests, therefore the mask was washed in clean water and dried between each test.
The intent of this test method was to a achieve a method similar to ISO 22609 Clothing for protection against infectious agents – Medical face masks – Test method for resistance against penetration by synthetic blood (fixed volume, horizontally projected).
All liquid penetration tests were performed under nominal recorded ambient conditions of relative humidity (52 ± 10) %; room temperature (20.0 ± 0.4) °C.
Three separate batches of synthetic blood were used throughout the testing of all samples, the surface tension of which was measured using the capillary rise method.
The results of the surface tension measurements of each batch of synthetic blood used for the liquid penetration tests are shown in Table 1 below.
The surface tension of synthetic blood described in ISO 22609 is 42±2 mN m-1, as measured according to ISO 304. The method of measuring surface tension used when mixing the blood used in these tests was the Capillary Rise method, as opposed to the Du Nuoy Ring method described in ISO 304. In the ASTM F1862/F1862M [Standard Test Method for Resistance of Medical Face Masks to Penetration by Synthetic Blood] Standard, section 18.104.22.168 states that the expected surface tension of the appropriate blood as measured using the Capillary Rise method is 61 mN m-1. This is corroborated in Portnoff, L., Jaques, P.A. and Furlong, J.L., 2019. The Surface Tension of Synthetic Blood Used for ASTM F1670 Penetration Tests. Journal of Testing and Evaluation, 47(2), pp.1635-1644.
The results of the liquid penetration tests of the filter material only are show in Table 2 below.
The results of the liquid penetration tests of the full mask assembly are show in Table 3 below.
The results and uncertainties given in this report are valid for the specified samples tested and refer to the measurements made during testing only.