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: In less than 1 hour after the ingestion of alcohol , he developed malaise with flushing of the face , tachycardia , and dyspnea .
### Output Text:
In less than 1 hour after the ingestion of <span class="chemical">alcohol</span> , he developed malaise with flushing of the face , tachycardia , and dyspnea . 