Technically yes. It's a gas, so it'll permeate through anything that's gas-permeable. And being a noble gas, it's pretty small, not as small as Helium, but stil

Technically yes. It's a gas, so it'll permeate through anything that's gas-permeable. And being a noble gas, it's pretty small, not as small as Helium, but still it'll wander right through membranes that're gas-tight for diatomic molecules and larger compounds. However, that is almost always a rounding-error in terms of basement soil-gas infiltration. You can sometimes feel a literal breeze coming through a crack if the house is badly depressurized (windy day and stack-effect), you will never feel a breeze coming straight through a solid concrete or cinder-block wall. The spikes probably come from depressurization events like that. Sometimes the wind is angled in such a way that the house effectively forms a whistle or a manometer, and soil gas migrates at a greater rate during those times. This is somewhere that _passive_ sub-slab ventilation (drill a hole, connect a vent pipe to the outside, no fan) can often help significantly, along with caulking all the cracks. Seriously, don't bother with anything else until you've caulked.