Wadrobes don’t like to stay dry and often attract unwanted scents (and sometimes creatures). Once easy way to solve the problem? According to how-to illlustrator Yumi Sakugawa, the answer is chalk. 
Chalk absorbs moisture, as many sources attest, so it’s a helpful aid to reduce dampness — and the resulting smell in your wardrobes. Just tie up a bundle with some sturdy string and hang it where it won’t brush up against your clothes. It will absorb moisture and the resulting smell.
real chalk is calcium carbonate but blackboard chalk which seems to be what is shown here is calcium sulphate which is a dessicant.