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: Low - risk controls ( n = 24 ) reported no parental history of hypertension and had screening BP < 130 / 85 mm Hg .
### Output Text:
Low - risk controls ( n = 24 ) reported no parental history of hypertension and had screening BP < 130 / 85 mm Hg . 