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: One burn site was treated with each of four different CHP concentrations , from 0 . 25 per cent to 2 per cent , their vehicle , and 1 per cent silver sulphadiazine ( AgSD ) cream , an antimicrobial agent frequently used for topical treatment of burn wounds .
### Output Text:
One burn site was treated with each of four different <span class="chemical">CHP</span> concentrations , from 0 . 25 per cent to 2 per cent , their vehicle , and 1 per cent <span class="chemical">silver sulphadiazine</span> ( <span class="chemical">AgSD</span> ) cream , an antimicrobial agent frequently used for topical treatment of burn wounds . 