WasteMaster is possibly the most robust system on the market and will continue to operate even if contaminates (such as a large plastic bag) are mixed in with the waste. However, the more contamination the less efficient the system will be. If the contamination level gets too high it may require an engineer to attend, which may incur a charge if it happens on a regular basis. We have seen items such as a silver teapot go through the machine and not cause any problems (apart from the teapot being damaged). Any small contaminates are seived at the receiving end as part of their process.