The first quarter was a tight affair as both sides struggled to make serious ground on offense, with the Steelers being limited to a couple of Shaun Suisham field goals to take the lead.
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The Falcons finally got themselves on the scoreboard with just over four minutes left of the first half, Ryan floating a 17-yard pass over for Devin Hester to haul in at the back of the endzone.
The Steelers responded before the second quarter was out, however, with Bell finding a gap in the defence to stretch over the line for a one-yard score.
Atlanta set about chipping away at the lead after the break, with Matt Bryant adding two short field goals to make it a seven-point game.
However, Bell got his second touchdown of the match when he looped round the defence and crept over in the corner to ensure that his side remained in control of proceedings.
The Falcons stayed within a score when Roddy White and Ryan combined for a four-yard touchdown, but it wouldn't be enough as Pittsburgh held out for the victory.