The home side had to settle for a frustrating draw after spurning a number of good chances in the second half.
Coming off three straight defeats, the Dynamo came out with renewed purpose in the first half, and created a number of good chances. Will Bruin's drive off the outside of the near post in the 38th minute was the closest either side came to scoring in the opening half.
The Union came out much stronger to start the second half, and Conor Casey and Amobi Okugo both spurned good chances to score in the half's opening 10 minutes.
With just over 10 minutes to play Kofi Sarkodie was sent off after earning a second yellow card for time wasting. Buoyed by their man advantage, the Union pushed for a winner but couldn't find one, as Andrew Wenger spurned the best chance when he blasted over the net from close range in injury time.