Paul Mennen wrote:
PV=nRT

I don't think that equation has much relevance here.

It most certainly does!
since nR=(P1V1)/T1=(P2V2)/T2
Where P1, V1, T1 can be the exterior conditions, and
where P2, V2, T2 are the interior conditions
it shows the relationships between the variables
changing any one variable, alters the other five