BFE (bacterial filtration efficiency) is a metric used to test the effectiveness of masks and respirators. Testing agencies typically use ASTM F2101 or EN 14683 standards to evaluate a product's performance in filtering bacteria. Next, I will introduce in detail the main steps and requirements of the testing process.
1. Sample preparation:
First, the testing agency will select a certain number of masks or respirators as samples. These samples are typically products produced by manufacturers prior to compliance testing. The selection of the sample size is based on statistical principles to ensure that the test results are representative.
2. Prepare bacterial suspension:
The BFE test uses Escherichia coli as the test organism. Testing institutions are required to prepare bacterial suspensions of specified concentrations for testing. Typically, bacterial suspensions are diluted with buffered saline to ensure that the number of bacteria exposed to each sample is within a specified range.
3. Assemble test equipment:
The test device consists of an airflow generator that produces a fixed flow rate and a bacterial collection device that surrounds the sample. An airflow generator passes test air through the sample, while a collection device collects the filtered bacteria.
4. Implement the test:
Secure the sample to the test equipment, making sure it completely covers the test area. Then, the air flow generator generates a certain flow rate of air through the sample. Bacteria are filtered as they pass through the sample, and a portion is collected in a bacteria collection device.
5. Bacterial count:
After the test, the bacteria in the collection device are extracted and counted using biotechnological methods. This can help determine how much bacteria was filtered out during the test.
6. Calculate bacterial filtration efficiency:
Calculate bacterial filtration efficiency (BFE) using the following formula:
BFE(%) = (1 - the number of bacteria filtered out after the bacteria pass through the sample / the number of bacteria before the bacteria pass through the sample) × 100
7. Repeat the test:
In order to ensure the accuracy of test results, testing agencies usually conduct multiple tests on each sample and calculate the average and standard deviation. This helps assess product consistency and reliability.
Through the above steps, testing organizations can evaluate the performance of masks and respirators in filtering bacteria. These tests help consumers and healthcare organizations select appropriate protective equipment and ensure it meets specified safety performance requirements. Note that the BFE test focuses on bacterial filtration efficiency, not virus filtration effectiveness. Testing of virus filtering effectiveness often uses different standards and test methods.