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 : Although angiotensin - converting enzyme inhibitor therapy reduces mortality rates in patients with congestive heart failure ( CHF ) , it may also cause decreased renal function .
### Output Text:
BACKGROUND : Although <span class="chemical">angiotensin</span> - converting enzyme inhibitor therapy reduces mortality rates in patients with congestive heart failure ( CHF ) , it may also cause decreased renal function . 