Airdrie survived more than half the game with 10 men following Kevin Green's dismissal to secure a draw at Dumbarton.
The Sons took the lead after 29 minutes when Craig Hill upended Patrick Walker in the area and Mark Gilhaney slotted home his third goal of the season from the penalty spot.
However, United responded quickly when Jamie Stevenson slotted Rhys Devlin's throughball past Stephen Grindlay to equalise.
All the Diamonds' good work was undone soon after, though, when Green hacked down Bryan Prunty in the 40th minute and was shown a red card.
Dumbarton dominated possession after the break but could not find the winner as Airdrie settled for a hard-fought point.
Dumbarton: Grindlay, Nugent, Lithgow, McNiff, Creaney, Gilhaney, Nicoll (Wallace 60), Agnew, McKinnon, Walker, Prunty (Winters 69). Subs Not Used: Ewings, Borris, Brannan.
Booked: Creaney, Nicoll, Agnew.
Goals: Gilhaney 29 pen.
Airdrie Utd: Fairley, Bain, Hill, Green, Lovering, Keast (Owens 89), Devlin, Lynch, Stevenson, Donnelly (Morton 75), Holmes. Subs Not Used: Duncan, Malone, Blockley.
Sent Off: Green (39). Booked: Hill, Devlin, Stevenson, Morton.
Goals: Stevenson 37.
Ref: David Somers