Wow... let's do the math...
Let's establish some numbers first.
Let's assume this guy only needs 1kg of Hydrogen.
Density of Air (Dair) = 1.225 kg/m3
Percentage of Hydrogen in the Atmosphere (PH) = 0.000055%
Let Mair rep. mass of air.
Let Vair rep. volume of air.
The amount of air this guy has to sift through (in kg) to get 1 single kilogram of hydrogen is:
Mair * PH = 1kg
Mair = 1kg / PH
Mair ≈ 18000 kg
The volume of air this guy has to sift through is:
Mair/ Dair = Vair
Vair ≈ 15000 m3
That is roughly 6 Olympic sized swimming pools! Just for 1 kg of Hydrogen!
As to why 1 kilogram of Hydrogen is important, when it reacts to oxygen, like in an explosion, it releases a lot of energy!!!
Here are some more numbers.
1 kg of Hydrogen reacting with 8kg of Oxygen = 121 Mega Joules
1 kg of TNT exploding = 4.18 Mega Joules
1 kg of Hydrogen releases roughly the same amount of energy as 30 kg of TNT.
I'm no demolitions expert, but I'm going to assume that 30 kg of TNT can do the job of kersploding those boulders depending on application, like drilling and setting charges.
Like, how fast is this guy filtering the air of Hydrogen!? Maybe there are simpler ways he's getting it, like reacting certain compounds in the air to produce hydrogen? Who the hell knows!?