A chameleon needs water to drink and to keep the humidity in its skin at the right level. Air humidity will provide the proper humidity for its skin, this is especially important when it sheds its skin.
Keeping the air humidity up
You can keep the relative air humidity (RH) up by spraying water into the enclosure of your chameleon. You can do this by hand with a plant mister or automatically with an electric fog machine / humidifier (“fogger”) or slowly dripping device (“dripper”). The fogger will release a fine mist of water at regular intervals. The dripper will just slowing release drops of water. A fogger works much better than a dripper for keeping the air humidity up. A fogger is much more complicated and expensive than a dripper though. Misting by hand can also work just fine when you are at home often.
How quickly the air humidity changes depends on the amount of ventilation, on the general air humidity of the area surrounding the enclosure, the temperature and the way you choose to heat the enclosure.
Measuring the relative air humidity
It is very important that you measure the air humidity and not just spray randomly. A hygrometer measures the air humidity and is a very cheap instrument to buy. You should not keep a chameleon without one of those. Relative air humidity differs between 0 and 100%. A measure of 100% relative air humidity means that the air is completely saturated with water. If you would take this air and heat it a little bit, the relative air humidity will go down because air with higher temperature can absorb more water vapor before it is saturated. That’s why we are taking about relative air humidity.
Most houses are within the 40 to 60% relative air humidity. This is normal for us but is a bit too low for chameleons. A veiled chameleon needs a RH of 50 to 80%. Better err on the side of too high than too low. Too high can cause fungus to grow, this can be unhealthy for you and your chameleon. Too low means that your chameleon could get dehydrated easily.
Drinking water for chameleons
Air humidity is very important for veiled chameleons, but it does not provide them with drinking water. It will not absorb the air humidity to use in its body. So to get some liquid in, it needs to drink. Read about drinking water for chameleons here.