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: As a function of dose , FZP first protected against convulsions and death .
### Output Text:
As a function of dose , <span class="chemical">FZP</span> first protected against convulsions and death . 