Vacuum bag filters a hot tip for mask safety during Covid-19

T-shirt buffs and scarves are only a little better than no mask at all, researchers have warned.

There is, however, is a simple solution for people observing Covid-19 safety protocols, and that is to insert a clean vacuum bag liner into a cloth mask.

Research published in the Journal of Hospital Infection by experts in the US and UK assessed the effectiveness of various mask materials to protect a person from infection after 30 seconds and after 20 minutes of exposure in a highly contaminated environment.

These included situations in a room with a patient with Covid-19 when no mask was worn, when an FFP2 (N95) respirator, FFP3 (N99) respirator or surgical mask was worn, and when a non-traditional material mask (silk, tea towel, vacuum cleaner bag, pillowcase, antimicrobial pillowcase, cotton mix, 100% cotton T-shirt, linen or scarf) was worn.

“While various materials are effective for filtering large droplets, aerosols generated from sneezing, coughing and aerosol-generating procedures may pass more readily through materials or leakage points,” the study found.

The greatest reduction in estimated mean risk of infection was with FFP3 masks, which reduced baseline mean risks by 94% and 99% for 20-minute and 30-second exposures respectively.

Of the non-traditional materials, the vacuum cleaner bag resulted in the greatest reduction in mean risk of infection (20-minute exposure 58%, 30-seconds exposure 83%), while scarves offered the lowest reduction (20-minute exposure 24%, 30-seconds exposure 44%).

Commenting on the study, SA experts recommended the use of multilayered material face masks.

“Having a multilayered mask will provide more protection,” said Prof Shabir Madhi, lead researcher on the Covid-19 vaccine trial.

Dr Angelique Coetzee, president of the SA Medical Association (Sama), said cloth face masks should have three layers comprising an outer, inner and middle or filter layer.

The outer layer should be a thicker woven fabric that is hydrophobic or water-resistant.

The inner layer must not inhibit breathing.

The middle or filter layer should be big enough to cover fluid excretions exiting from the mouth during coughing or sneezing, said Coetzee. It should also not inhibit breathing.

The researchers noted that limitations to the study include not accounting for viral transfer from the hands to the mask during mask adjustments, and assuming that all masks were worn in the same way. They added that realistically, the fit of homemade masks is likely to be more variable than the fit of regulated masks.

The report concluded: “This study demonstrated that some materials, such as vacuum cleaner bags, may be effective alternatives to reduce the risk of infection. While N95 masks (and similar respirators) are recommended for health-care workers and others in proximity to aerosol-generating procedures, alternative materials may be useful where there are shortages of personal protective equipment (PPE). This may be of particular relevance in low resource settings where access to PPE is considerably more limited.”

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