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: Continuously nebulized albuterol in severe exacerbations of asthma in adults : a case - controlled study .
### Output Text:
Continuously nebulized <span class="chemical">albuterol</span> in severe exacerbations of asthma in adults : a case - controlled study . 