The young Airdrie club were in danger of becoming cut adrift at the bottom of the division and needed a good start to the game, something Scott Fraser stepped up and delivered with a little more than two minutes on the clock.
After Brechin's Colin Hamilton fouled on the outskirts of his own penalty area, Fraser despatched the resulting spot kick, finding the bottom corner with his left foot.
Buoyed by their early goal, the home side kept the pressure on Brechin, whose sloppy marking allowed David Proctor to double Airdrieonians' lead on the 20-minute mark, nodding in from close range.
Gary Bollan had his men keep the ball well after notching their second and the Diamonds finished the first half in full control of proceedings.
Things did not get much better for Brechin after the restart, with Hamilton this time conceding a corner under pressure. Keigan Parker's delivery was met by James Lister, who found yet another gap at the heart of the Brechin defence.
The home side put the icing on the cake with 15 minutes of the game remaining, Liam Watt setting up Nathan Blockley whose crucial goal from the outside of the box made it 4-0 and moved Airdrieonians out of the relegation zone on goal difference.