Irwin and RSL goalkeeper Nick Rimando are tied for second in the MLS with six clean sheets.
Colorado (2-4-8) and Real Salt Lake (4-5-6) snapped two-game losing streaks.
Both team had good scoring chances in the closing minutes. Colorado's Dillon Powers missed a penalty shot in the 89th minute. He stalled his approach and Rimando dove the wrong way, but his shot rolled wide. On the final play of the game, RSL's Javier Morales gathered a loose ball near the penalty spot, but his shot deflected just wide.
Rimando has faced five penalty kicks this season and has only conceded two goals.