Buy a bag of potato chips at sea level and drive up to the mountain, and the bag inflates and may even burst. Buy a bag at altitude, and it is normal. Do the chip manufacturers adjust the amount of air in the bag based on the altitude of the store it is going to? What gives?
If the bag stays at altitude it will deflate. In Denver my son can which chips are the freshes. the bag will be inflated about to pop.
Aren’t the bags sealed?
Yes but the gas can escape over time through the walls of the bags. Much as a baloon goes flat over time.
It’s fun to take them on the airplane too.
I once took a roll-on deodorant in a plane up onto the Tibetan plateau. The first time I tried to use it, the ball popped out and shot across the room.
That why there a little hole in the top of the aerosol ones. To keep the caps from popping off when they deliver them to high altitude places.
Those little yogurts explode a bit when you open them up here – I’m at about 5800 feet. It’s annoying but can be funny on occasion.
I live at 11,200 feet. I have had bags burst coming from 9800 feet up to my house. It is a good question. I suppose most bags are just leaky enough that it is generally not an issue.
Ice cream can be a problem too. It’s full of air.
And stuff like lotion and sun screen. Go on vacation at sea level, and then open the container at altitude. Splurt.
I once drove a rental car from Dallas to Colorado Springs, CO in a day. Somewhere near the OK/CO border, the speedometer needle stopped working. It was like it was stuck. This continued for the rest of the trip to Colorado Springs.
The next day, the needle moved fine.
I concluded that the gauge compartment was ALMOST air-tight, and on he drive up the plastic had bowed out and distorted because of the decreased air pressure, causing the speedometer needle to bind and stick. Over night, the pressure equalized and the speedo worked fine.
The technique we use on the airplane to avoid wearing the yogurt is to first punch a single hole in the yogurt’s foil cap using a fork tine. No splurting.