It is one thing to need to add 5% to 10% of the pressure needed to "top-off" your tires. If however you have lost significant amount of air (20% or more ) and had been driving on the tire before discovering it there might be damage to the tire structure which could result in an explosive rupture when re-inflating.
This is especially true for steel body tires. A
tire shop safety cage is the ONLY way a steel body tire should be inflated if the tire was ever run with low air.
https://www.caba.biz/Portals/9/Zippe...ll%20Chart.pdf