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: BACKGROUND : TEE is a semi - invasive tool broadly used and its utilization associated to sedatives drugs might to affect the procedure safety .
### Output Text:
BACKGROUND : TEE is a semi - invasive tool broadly used and its utilization associated to sedatives drugs might to affect the procedure safety . 