Are these ansi z87 approved?

Yes. The 3M Solus 1000 Protective Eyewear meets ANSI Z87.1-2015 impact requirements.

I bought the wrong one. Can i purchase the foam gasket and headband separate?

Hi Kevin! Thanks for your question! YES - they are available.Here is the link to the strap: https://www.amazon.com/3M-70071694569-Solus-Replacement-Strap/dp/B01DEPO4JK/ref=sr_1_1?ie=UTF8&qid=1499981229&sr=8-1&keywords=B01DEPO4JKHere is the link to the foam gasket: https://www.amazon.com/3M-Solus-Replacement-Foam-Gasket/dp/B01DEPO436/ref=sr_1_1?s=industrial&ie=UTF8&qid=1499981357&sr=1-1&keywords=B01DEPO436I hope this is helpful. Thanks!

Absorb 99% uv a,b, and c?

Polycarbonate lens absorbs 99.9% of UVA and UVB rays. Thank you.

Do these form a complete seal around your eyes without gaps in the vents to keep out aerosol spray?

Are you referring to aerosol spray such as dentistry? If so, I ordered these for my orthodontic assistants. I am an orthodontist. They have a good seal when you use the strap. There are some small openings that allow for some ventilation to prevent fogging.