# What is node contamination

> Learn why a proxy IP's past use cannot be fully verified, what node contamination means, and where to find Merca's node setup and cancellation guides.

Source: https://merca.getchrovia.com/en/docs/node-contamination

A node is like a phone number. You can't be sure nobody used it before, because that history isn't fully traceable. The same is true of an IP: you cannot audit everyone who used it, so there is no fully clean node.

Buy from a reputable provider. Large pools make it less likely that the same IP was used before, and safer. To add one in Merca, see [Add a node](https://merca.getchrovia.com/en/docs/import-node). For which type, see [How to tell node types apart](https://merca.getchrovia.com/en/docs/node-types).

If you cancel later, see [Can someone else use a node I cancelled](https://merca.getchrovia.com/en/docs/cancelled-node).