Most people bring oxygen tanks with them because of the high altitude and the thinness of the air (the oxygen at the top of Mount Everest is about 1/3 that it is at sea level). But a very few people have made it to the top without them.
if you are in need of a gas mask, you BP isn't an issue. the mask may inhibit your ease breathing but it will not directly affect your BP.
You needed to take a gas mask in case their was a gas attack.
Gas mask was created in 1914.
you need to get it a gas mask
Gas masks were gradually developed in the 1800s and the exact year you need is in the link below.
I think it stopped gas getting in the mask...
A person wearing a gas mask.
Click on the blue shirt in the top right corner. Then click on the mask, but you don't need it.
A gas mask is used to filter out toxic agents in the air.
The main part of the gas mask is made out of rubber.
A gas mask
M65 Gas Mask.