In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The long - term safety of danazol in women with hereditary angioedema .
### Output Text:
The long - term safety of <span class="chemical">danazol</span> in women with hereditary angioedema . 