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Prices of Masks Vary over 100 Times – Bacterial Filtration Efficiency of 2 Samples Lagging behind Basic Barrier Protection Level

  • 2017.12.14
The 2003 SARS brought the issue of public hygiene into instant public prominence, that wearing masks can reduce the spread of droplet-transmissible diseases, for example seasonal influenza. It is, however, hard to differentiate a mask of good quality merely by sight and touch.  But help is at hand with a Consumer Council test on 29 mask samples. The quality of some samples left much to be desired. One sample in particular scored the lowest 1-point rating in nearly all test items; a few others also failed to measure up to their own claims in Bacterial Filtration Efficiency (BFE) falling short of the US American Society for Testing and Materials (ASTM) F2100-11 Surgical Mask Level 1 barrier protection, and raising doubts about the very effectiveness of the products.
 
The test examined the samples for BFE, Particle Filtration Efficiency (PFE), Differential Pressure, and Synthetic Blood Penetration Resistance, while inspected if product information was complete on the packaging; among them the more important items are BFE and PFE which were given more weighting in the rating. The results showed 13 of the samples to perform well scoring the top overall rating of 5 points, 11 samples 4.5 points but, on the other end of the scale, 2 samples scored poorly with 2 points and 1 point respectively. 
 
The ASTM F2100-11 standard divides masks into three levels – Level 1 Barrier, Level 2 Barrier and Level 3 Barrier. The BFE of ASTM Level 1 Barrier surgical mask shall be greater than or equal to 95%. In the test, 3 samples stood out among all with a BFE of more than 99.9%. In sharp contrast, the sample with the least overall rating of 1 point its BFE was a disappointing 60.4% while another with the claim "highly effective bacterial filtration" its BFE turned out to be 88.5%. Both samples were in not conform with the ASTM Level 1 Barrier BFE requirement greater than or equal to 95%. Further, 2 other samples that made claims of over 99% BFE were measured to be only 97.4% and 96.8% respectively.
 
Regarding PFE, the least performing sample was found to have a particle filtration rate of 38.6% only. Otherwise, all the remainder samples achieved a PFE of above 95% among them 23 samples even up to 99% in particle filtration.
 
The test also found vast variation in price, ranging from an average of $0.25 to $36 per unit, a staggering price differential of 140 times. But the most pricey sample is designed additionally for re-use and warmth retention purposes so is different from the ordinary masks. Excluding that sample, the second most highly-priced sample cost $13, still a significant 50 times more expensive than the cheapest sample. In the test, the lowest-priced sample ($0.25) its BFE and PFE were respectively 60.4% and 38.6%, and overall rating was a mere 1 point. By comparison, the highest-priced sample ($36) scored an overall rating of 3.5 points, whereas another sample ($0.75) was one of the top performers in overall rating with a maximum of 5 points. Clearly, no direct correlation between price and quality of the product could be established in the test.
 
The Council, at the same time, uncovered the labelling in most samples were lacking in clear and complete product information. Some were without place of origin, expiry date, user reminder not to re-use the mask, proper way to dispose of the mask after use, its BFE and PEF, etc. while a few were mainly in Japanese only. Suppliers are urged to pay attention to packaging labelling information for improvement.
 
Variation was detected also in the tests on Differential Pressure (Breathability) and Synthetic Blood Penetration Resistance (Fluids Penetration Resistance). According to the ASTM F2100-11, the Differential Pressure of ASTM Level 2 Barrier surgical masks should be under 5.0 mm H2O/cm2, exceeding that standard may lead to affect the breathability of the wearer. 2 of the samples were measured to have Differential Pressure of 6.5 and 7.9 mm H2O/cm2.
 
In the latter, most masks were found with satisfactory fluids penetration resistance prosperity. Only 2 samples were of a weaker performance but this particular test is designed to simulate the scenario when healthcare workers are performing procedures with blood or body fluid splashing risk is reasonably anticipated. In daily life of ordinary people this scenario is relative rare.
 
Consumers wearing masks should pay heed to the following:
  • Use soap and water or alcohol hand rub to clean hands before wearing a mask;
  • Don't touch the mask with your hand(s) to avoid contacting the pathogens that may be on the mask; 
  • Change to a new one when it is wet;
  • Do not leave used mask around or in the pocket for re-use;
  • Masks that are washed for re-use may not be suitable for communicable disease prevention purposes;
  • Dispose of the mask immediately after use into lidded rubbish bin, and perform hand hygiene;
  • Surgical masks are not designed for filtration against particulate matter (PM2.5) air pollution pollutants; wearing a mask for prevention of such hazard is not appropriate.
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