Prevent rule from triggering on Entity Reference Fields I am trying to add a rule that does something when the user views my content type "contacts", so I used the "Content is viewed of type" event to trigger the rule.

Contacts can also be added to other nodes via the Entity Reference Field. Eg. for the content type "events" you can add the contact in charge of it.

Problem is now that this rule also triggers for content type "events", cause of the "contacts" reference.

How can I prevent that?
It shouldn't fire because of an entity reference field.. 

Have you added a Content is of type  condition to the rule?

Data selector: node
Value: Contacts. 

Edit:

It could be that the display mode of the referenced entities is counting as a view. 

Add a condition, data comparison for site:current-page:url and node:url 

This will force rules to check the page url which will return FALSE for every page except the nodes's pages.