IANAL, but in the US if you know about a patent and infringe upon it then that's considered "willful" infringement and they can triple the damages against you. Therefore many people in your position don't look at any patents whatsoever so they can plead innocence if a patent infringement occurs and minimize any potiential settlement. If you start looking for and reading over patents to try and cover your ass, you may end up digging a deeper hole later on. Given the huge number and scope of some patents, even if you do look you may miss one or think that one doesn't apply when a lawyer/judge thinks otherwise. If you start pulling in large amounts of cash, keep a good laywer on retainer and pray none of the big guys with large portfolios decide to come after you.