The Spireites were on course for a victory when Martin Gritton fired them ahead in the 77th minute, but Sam Saunders converted a corner in the third minute of injury time to earn a point for the Daggers.
Richardson said: "It's similar to last week at Wycombe and it feels like a defeat when you've had victory snatched from your grasp.
"I think it illustrates the nature of this division. Matches are so tight at times and when you are only one goal in front there's always concern.
"But I think we must have conceded close to double figures in points now through injury-time goals. It happened at Wycombe and now again here so it's a massive disappointment."