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 recognition of angiotensin - converting enzyme ( ACE ) and angiotensin receptor blocker ( ARB ) intestinal angioedema constitutes a challenge to primary care physicians , internists , emergency room personal and surgeons .
### Output Text:
The recognition of <span class="chemical">angiotensin</span> - converting enzyme ( ACE ) and <span class="chemical">angiotensin</span> receptor blocker ( ARB ) intestinal angioedema constitutes a challenge to primary care physicians , internists , emergency room personal and surgeons . 