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: BACKGROUND : Hydrochlorofluorocarbons ( HCFCs ) are used increasingly in industry as substitutes for ozone - depleting chlorofluorocarbons ( CFCs ) .
### Output Text:
BACKGROUND : <span class="chemical">Hydrochlorofluorocarbons</span> ( <span class="chemical">HCFCs</span> ) are used increasingly in industry as substitutes for <span class="chemical">ozone</span> - depleting <span class="chemical">chlorofluorocarbons</span> ( <span class="chemical">CFCs</span> ) . 