You don’t need to change the water at all. Because the roots are living it will remain clear and not smell. It’s not like a cut flower. Keep the hyacinth in a very cool very light spot. No need to mist.

The smell is a question of personal preference, not health, unless someone is particularly sensitive.

When the flower fades you can plant the whole thing outside in the garden if you have one. If you don’t have a garden or outdoor container, water-grown hyacinths are effectively temporary decoration and are usually discarded after flowering. If you plant it outside just stick it in the ground, not in peat. It needs the soil nutrients to build up the bulb. It should flower outdoors in subsequent years if you live in an appropriate climate but the bloom will be less dense and more delicate.

re: Does the smell of hyacinth flower have any damage towards humans?

I'm relatively new to growing bulbs, but have worked a long time in analyzing the chemical makeup of plants, foods and aromas. Briefly, there's nothing out of the ordinary in the hyacinth volatile compounds. It's not any more dangerous than other floral scents. Phenylacetaldehyde gives it the distinctive smell in my opinion (it's in the same family as cinnamaldehyde and benzaldehyde, but has milder odor).

To add to what was mentioned above, certain chemicals & smells may provoke irritation etc in some individuals but not others. In a closed room with dozens of flowers in various stages of growth/decay, it could get overwhelming (too much of a good thing). Hope that helps.