Table. Ratio of ambient-to-device concentrations of 0.02- to 1-μm–diameter particles (median [range])^a.

Exercise	Stryker T4	Stackhouse FreedomAire	3M 8233 N100 mask with surgical mask and face shield
Normal breathing	4.5 (4–5)	3 (2–4)	32,550 (1,420–60,900)
Deep breathing	4.5 (4–5)	3 (2–3)	21,550 (4,150–99,300)
Head side to side	4 (4–5)	3 (2–3)	15,675 (681–138,000)
Head up and down	4 (3–5)	3 (2–3)	19,300 (380–138,000)
Talking	4 (3–5)	3 (2–3)	1,550 (394–18,200)
Bending over	3.5 (3–4)	2 (2–3)	7,695 (1,620–31,000)
Normal breathing	4 (3–5)	2.5 (2–3)	22,100 (4,670–163,000)
Fit factor	3.8 (3.7–4.8)	2.5 (2.0–3.1)	6,392 (962–50,519)

^aRatios for Stryker T4 and Stackhouse FreedomAire were significantly lower in all tests compared to the combination of N100 mask, surgical mask, and face shield (p <0.004.)