Does one brand of furnace filter trap more dust than another? Filters look similar on the shelf. But the materials inside may catch very different amounts of particles. You cut two filter brands in half. Weigh each half on a triple beam balance. Tape one half of brand A to one half of brand B. Both halves sit side by side in the same furnace. Leave the filters in place for one week. Then remove them and weigh each half again. The difference in mass shows how many particles each brand collected. Repeat the trial three to four times. Brand A gained more mass than brand B in every trial. That means brand A trapped more airborne particles under the same conditions.