"If we want to become more professional we can't ignore it," he said.
"The reality is we have to get things right if we can - decisions could mean people get to hang on to their jobs. There is too much riding on these decisions for us to say we won't go back and have a look.
"Having a TMO is outstanding. If the process takes another 15 minutes then you can go and get another beer and a hotdog.
"Are referees erring on the side of conservative by calling for the TMO? Maybe they are, but isn't it better for everyone if we get the right decision?"
For some time Kirwan has advocated two referees should control games, as they did in rugby league.
The more officials got right, the better. It added rather than detracted from matches.
Overturning the original penalty-only ruling on Nonu was a case of the referee getting it right.
Another senior referee, Jonathan Kaplan, also used the referral system several times on Saturday during the Hurricanes match with the Waratahs.
Incidents could be a blur as players raced around the field at more than 30km/h and match officials needed help so their calls meshed with what audiences saw on television.
"When we played the Waratahs we had three key decisions go against us that cost us 10 points and none of them were looked at by the TMO," said Kirwan.