You get problems with your blood circulation and not enough oxygen goes to your brains, and that's why you faint.

你的血液循环有问题,没有足够的氧气提供给脑部，这就是为什么你会晕眩。

youdao

She advises, "You don't want to sign up for a $10,000 vet tech course only to find out later that you faint at the sight of puppy blood!"

她建议说，“你也不想报名上了一万美金的兽医课，结果只发现你晕血！”

youdao

I saw you faint in the office.

我看到你在办公室昏倒了。

youdao

I'm going to talk for a while. (Laughter.) You guys don't sit down because you don't have chairs. (Laughter.) But you guys all have to bend your knees a little bit so you don't faint.

WHITEHOUSE: The White House

You can also activate a (fairly faint) beeper, and an LED ring around the perimeter of the sticker, further helping you to find the device, even in a dark room.

ENGADGET: StickNFind Bluetooth stickers let you tag and locate your goods with a smartphone (hands-on video)

You should also see a very faint white layer of mannite, a natural powder that is a carbohydrate and source of sweetness.

WSJ: Kelp Wanted