Sorry for the delay in answering this post.  I missed it.

In talking with our resident oxygen guru, Batch, he and I collaborated with the following answer:

The reason that the 3 liter bag works so well is that your lungs can usually only take in around 3 liters of air during a maximum inhale.  Yes, your lungs hold more than 3 liters, the average adult lung capacity is about 5 liters.  

In your normal abort method, (using one of those cheap disposable masks at only 15 LPM) you will only be pulling in around 1 liters of oxygen, per inhale.  That is only 20% of your normal lung capacity.  So with the 3 liter bag, you are up to 60% with a maximum inhale, which gives you a much greater ventilation of the lung.

The goal of this therapy is to cast off CO₂ faster than your body is producing it.  This is the main idea behind hyperventilating, with the higher flow rate and 3 liter bag.

When you are just sitting there, watching TV, or surfing the net, you are only taking in about 1/2 to 3/4 a liter of air, at a time.

I hope this answers your question.

BTW, Deej now has his resupply of masks, so those that were waiting, he has them on hand now.

Chuck