There aren't, and aren't likely to be, regulations prohibiting a homeowner from a foolhardy practice such as heating the kitchen with a gas range turned on high. Likewise heating systems about which any scientists are skeptical, such as unvented space heaters, are quite common. You should be aware, however, that even in the absence of carbon monoxide, such an appliance could be contributing to chronic health problems your family members may have. And should an unvented heater malfunction, it could be life-threatening. If you have a woodstove or an oil furnace that backdrafts, you're probably aware of it.
Wood smoke is visible and fuel-oil furnaces provide a telltale whiff of sulfur to the nose.
Unfortunately, gas appliances don't offer such ready hints. In any event, if backdrafting has been occurring often in fossil-fuel burner, there should be some signs on the appliance itself. If they're extensive, you've been having at least some spillage. On a gas furnace or water heater, look at the outlet from the unit. There will be a cone-shaped hood there that admits extra air to the chimney to stabilize draft, and soot will show up around it if the appliance has been backdrafting significantly.