Poisoning in your catalyst occurs when some substance in your air stream, such as silicone or an oil, reacts with your catalyst and forms a bond with it rather than releasing back to the air stream. The bond covers the precious metal and prevents further exposure to the incoming air stream. Other substances my simply mask your catalyst by sticking to it or coating it. These substances can be “washed” to rejuvenate your catalyst. Poisoning or masking in your catalyst causes a risk of non-compliance.