Mix 40 g of sodium chloride in 100 ml of water. If you can't tell if the solution is saturated, stop here and do not proceed. If you're sure that the solution is saturated, decant it into the gas bubbler.
Bubble ammonia gas in the fume hood through the saturated sodium chloride solution. It should only take a couple of minutes to saturate the solution with ammonia gas. Be sure to catch the excess ammonia in a gas trap.
With the chemicals still in the fume hood, bubble carbon dioxide through the solution. The sodium bicarbonate will precipitate out.
Filter the sodium bicarbonate carefully from the solution using gravity filtration.
Allow to air dry. Properly dispose of the leftover solution which contains leftover ammonium chloride, sodium chloride and sodium carbonate.