6/4/2016 · Hach recommend that mercury free COD vials should only be used if Chloride and Ammonia levels do not exceed those stated below; Low range, 0-150 mg/L – Chloride 0 – 100 mg/L – Ammonia 0 – 50 mg/L High range, 0-1500 mg/L – Chloride 0 – 200 mg/L