Reference:

Davies, Anna, Katy-Anne Thompson, Karthika Giri, George Kafatos, Jimmy Walker, and Allan Bennett. “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Disaster Medicine and Public Health Preparedness 7, no. 4 (May 22, 2013): 413–18. https://doi.org/10.1017/dmp.2013.43.

Experimental Design

This experiment had two parts, but only one was relevant to this graphic. Check out the second half of the experiment here.

The scientists put several types of household fabrics in a sealed box. Then, they created a mist filled with a virus called Bacteriophage MS2, and sprayed it into the box. They measured the concentration of virus before and after the mist passed through the fabric filter.

Results

Materials with lower thread counts did ok:

• 100% cotton T-shirts filtered 51% of viruses, but they are still good mask materials because they’re stretchy and easier to fit than materials with higher thread counts.
• Scarves filtered 49% of viruses

Materials with high thread counts performed better:

• Regular pillowcases filtered 57% of viruses
• Linen filtered 62% of viruses

Surgical masks and vacuum cleaner bags performed the best:

• Surgical masks filtered 89% of viruses
• Vacuum cleaner bags filtered 86% of viruses, BUT it is NOT a good idea to use them for masks! They can contain toxic materials, and might be too hard to breathe through!

What does this mean?

Surgical masks and high thread count fabrics are better at filtering viruses. But filtering ability isn’t the only indicator of what makes a good mask. For example, a well-made mask made from a cotton T-shirt fits better than a regular surgical mask, even though it doesn't filter as well. And even though vacuum cleaner bags are excellent filters, they are TERRIBLE MASKS.

Up Next: What are the best practices for mask-wearing?

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