Removing dog urine smell... grrr

[lorenz0]

So I am dog sitting right now 2 dogs and one is not trained (long story)

Even walking the dogs 3 - 4 times a day is not enough. Well after a month I am actually starting to get sick. My apartment doesn't have circulating air and it is starting to smell disgusting. I picked up a rug doctor tonight and cleaned the carpets using a general cleaner, which worked at making them look 100% better but it did not remove the smell. I also had my windows and patio door open for 4 hours in hope that it might help but nothing. Also tried febreeze oder neutralizer and that didn't work.

Any help would be very much appreciated