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: Seven out of 12 subjects experienced headache of a short duration accompanying facial flush in one and nausea in one , especially after ingestion of CLZ .
### Output Text:
Seven out of 12 subjects experienced headache of a short duration accompanying facial flush in one and nausea in one , especially after ingestion of <span class="chemical">CLZ</span> . 