No specific test for exposure - workup should be based on history and sypmtoms. Consider:
Laboratory studies (e.g. CBC, CMP, lactate)
Chest X-ray
ABG
Laboratory studies (e.g. CBC, CMP, lactate)
Chest X-ray
ABG
Phosgene
Blister chemical agents 
Levoleucovorin
Lewisite 
Tdap
Sulfur mustard 
PALS 
Phosgene oxime 