The director of the NIH Dr. Anthony Fauci has said it seems like common sense that wearing two masks is better than one. So we decided to test whether two layers of the same material is better than one layer.
Note that there may be other benefits of wearing double masks, such as an improved seal. We are only testing filtration performance of two layers versus one layer of the same material.
Test: Does Two Layers Improve Effectiveness?
Wearing two masks of the same material might have a smaller impact on its effectiveness than you’d think.
Scientists tested double-layered versions of DIY mask materials including a dish towel, pillow case, and 100% cotton shirt fabrics. The effectiveness of these masks against bacteria-size particles were tested both in a single and double layer.
Overall, doubling up the mask materials did not help much. The towel had the largest increase in effectiveness with a 14% increase, but the other cotton t-shirt and pillowcase only saw a 1-2% improvement.
Wearing Two Masks Reduces Breathability
One negative to doubling up and wearing two masks is it could make it feel harder to breathe. While wearing double masks of the same material modestly improves effectiveness, research shows it also decreases breathability.
As you can see, doubling up the masks into two-layers decreases breathability considerably. With two-layers, the dish towel mask was over twice as unbreathable as a surgical mask.