As fruit ripens it give off a gas. This gas speeds the ripening process. By placing the fruit in a bag or paper you capture and concentrate that gas and speed the process.
Other fruits will not be damaged if placed in a bag with a banana. However, other fruits will ripen faster when placed in a paper bag with a banana. Some may ripen so fast that they spoil.
You place them on the windowsill.
some fruits can ripen when exposed to high levels of CO2 or etilen which is a plant hormone (bet my spelling is wrong but that's how you say it).
they ripen quiker in sumer because it so hot that they start to blush
They give off a lot of ethylene gas and even make other fruits and vegetables stored with them rot or ripen quickly.
Pineapple
Frequently is used the ethylene oxide.
Pears ripen pretty quickly, but if you put in a bag with a banana or an apple the gases from these fruits will make the pear ripen quicker.
I think you mean an apple will ripen bananas or green tomatoes. The apples as they ripen give off gas that aids and speeds up the ripening of other fruits, like placed in a brown bag with bananas or tomatoes and other fruits. Apples stored in the frige crisper drawer will make other fruits ripen quickly, thus go bad before you use them too.
Kalburo is a chemical used to ripen the banana and mango fruits.
Bananas ripen quickly on their own as they're one of the few fruits that release ethene. Keeping them together in a plastic bag should make them ripen. Keep them away from other fruit that you don't want to go off, and if you want avocados to ripen put them in a brown paper bag with bananas in an airing cupboard.
Fruits ripen more quickly in cabinets due to the presence of ethylene gas, a natural plant hormone that triggers ripening. Refrigerators slow down this ripening process by reducing ethylene production and inhibiting ripening enzymes. The cold temperatures in the refrigerator also slow down the metabolic processes that lead to ripening.