Assuming it really is damp then bookbinder's answer is the best (spraying perfume on the thing will not dry it out). On the other hand, what you may be smelling is the beginnings of fungal growth. Again, putting the chair in the sun, or in any way that suits you warming it up will also help greatly. For some years to come it must be continually be kept in a really dry place or else the fungi will get going again. This means putting it and leaving it in a properly (i.e. not just occasionally) heated room during winter.