Dealing with... low ambient humidity
Relative excerpts from the above link, reader digested.
"Often, when snakes or lizards are showing signs of poor shedding due to their captive environment being too dry, owners seek ways to increase the overall humidity of the enclosure.
While this is necessary for certain species, such as rainbow boas and tropical rain- or cloud-forest chameleons, overall increases in the ambient enclosure humidity may result in adverse health problems.
... the growth of fungus and bacteria are not uncommon.
Instead, microclimate pockets of higher humidity can be provided for most reptiles.
For others, a slight increase in overall humidity levels coupled with bathing and spraying may be sufficient.
Increasing Ambient Humidity
...providing a large...water bowl will raise the humidity.
The water will more rapidly evaporate from the large surface area...
(Room Humififiers)
The ambient humidity in a reptile room or large walk-in enclosure may be provided by using one or more of the many inexpensive humidifiers that may be purchased at grocery and drug stores. These may be run 8-12 hours a day during the periods of driest weather, or daily, as needed.
... To get through periods of excessively dry heat (either in the winter or summer) spray bottles of water may be used to spray the reptiles and/or their environment....
Humidity retreat boxes may be easily made by taking a plastic food or clothing storage container with a fitted lid.
Cut a hole near the top of one side big enough for the lizard or snake to crawl into. Fill the box 2/3 full of damp sphagnum moss. Place the reptile into the box and place the lid on; they will find their way out of it. Thereafter, they will be able to enter and exit when they need to. Leave the box in the enclosure all the time, or place it in there in the middle of the thermal gradient, when you notice the reptile's color beginning to change as it enters the shedding period.
...keeping in mind that it will dry out faster in a warmer tank and when the ambient room humidity is low." ~M.K.~