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: A single - placebo - controlled oral challenge procedure with nimesulide or paracetamol was applied to 829 patients with a history of NSAID - induced urticaria / angioedema .
### Output Text:
A single - placebo - controlled oral challenge procedure with <span class="chemical">nimesulide</span> or <span class="chemical">paracetamol</span> was applied to 829 patients with a history of <span class="chemical">NSAID</span> - induced urticaria / angioedema . 