Best Seller | Combo Alert Pack, 1 Year Ammonia Alert is an innovative color device for continuously detecting and monitoring toxic free ammonia. A sensor changes reversibly from yellow to green to blue, relative to the ammonia concentration. No test kits, chemicals, or procedures are... ... more Combo Alert Pack, 1 Year Ammonia Alert is an innovative color device for continuously detecting and monitoring toxic free ammonia. A sensor changes reversibly from yellow to green to blue, relative to the ammonia concentration. No test kits, chemicals, or procedures are... Petco.com | | $15.43 go to store |