Anti Synthetic blood penetration testing Procedure

A specimen medical face mask is supported on an apparatus. A volume of synthetic blood is sprayed horizontally at the specimen mask to simulate the scenario of a mask being splashed by a punctured blood vessel. The volume of fluid, distance to impact, orifice size and fluid velocity are defined in this method and intended to be consistent with this health care scenario.

 

Preparation and cleaning of test apparatus

 

NOTE 1 

An alternative test set-up procedure is provided in 7.3 that utilizes a targeting plate to ensure a more accurate and uniform velocity of fluid to the specimen mask.

Prepare and clean the test apparatus using the following steps.

a) Install a clean 12,7 mm long canula with an inside diameter of 0,84 mm on the front of the pneumatic-controlled valve.

b) Fill the reservoir with new synthetic blood (approximately 1 l).

c) Set the valve time corresponding to the blood pressure being assessed in accordance with Table 1. If non-standard pressures, fluid volumes (2 ml) or canula sizes (0,084 cm ID) are employed, the valve time should be calculated using Equations (C.4) and (C.7) in Annex C.

 

NOTE 2 

For the purposes of this test method, as a minimum three different sets of specimens at stream velocities corresponding to blood pressures of 10,6 kPa, 16,0 kPa, and 21,3 kPa are evaluated.

d) Adjust the reservoir pressure as needed to achieve a flow of 2 ml for the selected valve time.

e) Verify the amount of synthetic blood delivered to be 2 ml by conducting trials into a graduated cylinder.

Alternatively, the volume of synthetic blood can be measured by determining the mass using a balance. For the standard fluid, with a specific gravity of 1,005, the 2 ml of fluid would weigh (2,010 ± 0,040) g.

f) After every 16 specimens, ensure that the text apparatus is delivering 2 ml of synthetic blood by following the method calibration steps as directed in 7.1 d) and 7.1 e).

g) If the canula is left unused for 1 h or more after synthetic blood has passed through it during testing, replace it with a clean canula and clean the used canula.

h) Clean the canula by immersing in isopropanol for 24 h and rinsing with distilled water.

i) Following testing, clean the system lines and the reservoir with distilled water. Do not use isopropanol or other solvents on the valve or system lines as the valve may be damaged.

 

Use the following steps to evaluate medical face masks.

a) Conduct all testing in an environment having a temperature of (21 ± 5) °C and a relative humidity of (85 ± 10) %.

b) Place a small droplet (approximately 0,1 ml) of the synthetic blood on the normal inside surface of an extra medical face mask. The droplet shall be easily visible to ensure that any droplet that penetrates the material will be seen. If not, use talcum powder on the normal inside surface of the medical face mask to enhance droplet visibility.

c) Remove a specimen from the conditioning chamber. Mount the specimen on the specimen-holding fixture and position the specimen for impact of the synthetic blood to occur in the target area.

If the face mask contains pleats, spread the pleats out when mounting the face mask onto the test fixture to present a single layer of material as the target area. Use the centre of the specimen as the target area.

Position the end of the pneumatic-controlled valve at a distance of (300 ± 10) mm from the target area from the specimen.

d) Squirt the synthetic blood onto the specimen medical face mask. Ensure that the synthetic blood hits the target area of the medical face mask. Conduct the test within 60 s after removal from conditioning chamber.

e) Inspect the viewing side of the specimen for synthetic blood (10 ± 1) s after squirting the synthetic blood against the target area. Note whether any synthetic blood or other evidence of wetness, or both, appears on the viewing side of the specimen using suitable lighting.

Use a cotton absorbent swab or similar item to lightly daub the target area if there is any doubt regarding the visible penetration of the synthetic blood.

f) Test the remaining specimens.

 

Alternative test set-up using a targeting plate

The following procedure improves the accuracy of the velocity of the stream hitting the target mask. Once the valve opens, the pressure of the fluid at the tip drops as frictional losses build as the fluid flows through the tubing, valve and canula. The net result is that the pressure of the initial portion of the stream can be two to three times the target pressure. This procedure blocks this high-pressure stream and allows only the fluid travelling at the target velocity to hit the mask.

a) Set the valve time to 0,5 s.

b) Collect and weigh the amount of fluid delivered from the nozzle.

c) Set the valve time to 1,5 s.

d) Collect and weigh the amount of fluid delivered from the nozzle.

e) Calculate the difference in mass of the two spurts. For a test fluid with a specific gravity of 1,005, Table 2 gives the target difference in mass plus lower and upper limits for a velocity range within 2 % of the target. See Annex B to determine the target mass differences for other velocities, canula sizes or fluids with other specific gravities.

f) Adjust the reservoir pressure as necessary and repeat steps 7.3 a) through 7.3 e) until the mass difference is within the target range.

g) Once the reservoir pressure has been set, do not change the relative height of the reservoir and nozzle.

h) The targeting plate should be placed approximately 1 cm away from the mask and be located such that the fluid passing through the hole in the targeting plate hits within 0,6 cm of the centre of the hole in the specimen holding form.

i) Adjust the aim of the valve assembly such that the steady-state portion of the stream passes cleanly through the targeting hole. The initial portion of the stream should hit above the hole.

j) Set the valve time to 0,5 s.

k) Collect and weigh the amount of fluid passing through the targeting hole.

l) Set the valve time to 1,5 s.

m) Collect and weigh the amount of fluid passing through the targeting hole.

n) The difference in mass between the 0,5 s and 1,5 s deliveries through the targeting plate hole should be within mml_m1 of the difference in mass from the nozzle [7.3 f)].

o) If the differential mass through the hole is less than 95 % of the mass difference exiting the nozzle, check the aim of the stream to make sure it is passing cleanly through the targeting hole.

p) If the mass differential is more than 102 % of the mass difference exiting the nozzle, repeat the collecting and weighing process in 7.3 a) to 7.3 f).

q) Adjust the timer setting until 2 ml of fluid passes through the hole for three spurts in a row. For a test fluid with a density of 1,005 g/cm3, the output should weigh 2,01 g.

r) Record the timer setting to use as the starting point for subsequent testing.