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 estimated incidence of angioedema during angiotensin - converting enzyme ( ACE ) inhibitor treatment is between 1 and 7 per thousand patients .
### Output Text:
The estimated incidence of angioedema during <span class="chemical">angiotensin - converting enzyme ( ACE ) inhibitor</span> treatment is between 1 and 7 per thousand patients . 