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Many assume that being indoors safeguards them from UV rays, but windows and certain glass materials cannot fully block UVA rays. Measurements inside homes show that UVA can penetrate through standard windows, especially when curtains are open or blinds are drawn.
Physical barriers such as blackout curtains, laminated windows, and UV-protective films significantly reduce UVA exposure indoors. For example, covering windows with laminated or frosted glass cuts down UVA transmission by up to 50-100%, dramatically decreasing indoor UV risk. Even laminated or tinted windows on cars shield occupants from a substantial portion of UVA rays—around 70-90%—though some exposure remains, especially for drivers.