safety - How does sulfuric acid react to heating?

How would $\ce{H2SO4}$ react to heat ? I assume that it would form toxic sulfur (di/tri)oxide, but I can't find any information on this.

I'm concerned about fire hazards specifically, so assume very intense heating and very low concentration.

Answer

Sulfuric acid, $\ce{H2SO4}$, having an enthalpy of formation of $-814$ kJ/mol, is quite stable and won't decompose easily.

According to A Kinetic Study of the Decomposition of Spent Sulfuric Acids at High Temperature, Dominique Schwartz, Roger Gadiou, Jean-François Brilhac, Gilles Prado, and Ginès Martinez:

The decomposition of $\ce{H2SO4}$ to $\ce{H2O}$ and $\ce{SO3}$ is predominant between $400$ and $700$ K. The formation of a small amount of gaseous sulfuric acid can be observed. Above $673$ K, the equilibrium constant of the reaction R1 becomes higher than 1 and increases rapidly.

$$\ce{H2SO4 <=> H2O + SO3}\tag{R1}$$

The second process is the reduction of sulfur trioxide to $\ce{SO2}$. This endothermic reaction needs a high temperature to take place, the equilibrium constant of the reaction R2 being higher that 1 above 1050 K.

$$\ce{SO3 <=> SO2 + \dfrac12O2}\tag{R2}$$

So, you only have to worry when the temperature reaches $400$ K, or $127^\circ\mathrm{C}$ (false precision).