Why does this researcher have a “clear plastic bag” over their head?

The Space.com article Astronauts Zip-Line to Safety in These NASA Emergency Evacuation Test Photos includes some interesting photos of the test. I show one of the photos below, plus sone cropped sections.

I'd like to understand why one researcher has what looks like a clear plastic bag on their head compared to the helmets on the two people serving as astronauts, and at least one person with nothing at all.

The caption for the photo:

Astronauts participate in a Boeing/United Launch Alliance (ULA) emergency-egress system demonstration at Cape Canaveral in Florida on June 19, 2018. The Boeing CST-100 Starliner will launch on a ULA Atlas V rocket, carrying astronauts to the International Space Station. Credit: Kim Shiflett/NASA/Flickr

click for full size

• I'm not sure why the final, full image is still showing as 640px wide, and not medium size. I'm using the recipe to make it appear small (append "m" to the filename) – uhoh Aug 8 '18 at 9:08
• Obligatory Johnny Space Commander reference: 2.bp.blogspot.com/-Gvm9EdKJREk/UJFFEfRfAmI/AAAAAAAADFg/… – Organic Marble Aug 8 '18 at 14:34
• It seems to be an issue with Imgur. All the sizes I've tested (m, l, t) show with the same dimensions as the full image, except for s which is too small at 90 x 90. – CJ Dennis Aug 9 '18 at 8:40
• @CJDennis thanks. I'll keep an eye on it now. – uhoh Aug 9 '18 at 9:48