The burning bar is limited as a burglar tool because:

The burning bar is restricted in its effectiveness as a burglary tool for several reasons. Firstly, it is not suitable for penetrating concrete, a common material in modern construction. Concrete's density and heat resistance make it impervious to the heat produced by a burning bar, limiting the scenarios where this tool can be successfully utilized.

Secondly, the actual heat output of a burning bar is often not intense enough to effectively cut through tougher materials, such as metals or reinforced structures that are commonly found in security barriers and safes.

Lastly, the burning bar typically requires hydrogen tanks for operation. This requirement presents logistical challenges and adds complexity to its use. It necessitates additional equipment that can limit its practicality in quick burglary situations.

All of these factors contribute to the conclusion that the burning bar is a limited tool for burglary, making the overall characterization of it being constrained by these specific limitations accurate.