Help! Used Pipe Drainer into Dishwasher.

Hello, I need some help please. My dishwasher was blocked so I had the 'brilliant' idea to put pipe drainer into it. Obviously it didn't help, we had to call an engineer which came after 15 days to fix it. The chemical stayed in the dishwasher for 15 days, after the engineer fixed it, I run 4x 70 degree cycles but I'm still worried it all the chemical had gone away. Please don't judge me, I was so silly to do that. What shall I do now, will the dishwasher be still contaminated? How can I make sure is cleaned and will it be ever safe to use again? Thanks a lot for any advise.