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 conclusion , CPA , diazepam and 2PAM in combination with atropine prevented the occurrence of serious signs of poisoning and thus reduced the toxicity of DFP in rat .
### Output Text:
In conclusion , <span class="chemical">CPA</span> , <span class="chemical">diazepam</span> and <span class="chemical">2PAM</span> in combination with <span class="chemical">atropine</span> prevented the occurrence of serious signs of poisoning and thus reduced the toxicity of <span class="chemical">DFP</span> in rat . 