Making carbon monoxide gas from formic acid and sulfuric acid?
The formation of carbon monoxide already takes place when mixing formic acid and sulfuric acid at room temperature, but the reaction is relatively slow. Since the temperature of the mixture may significantly increase during the course of the reaction, the reaction rate may increase, which makes the reaction difficult to control.

For laboratory applications, concentrated sulfuric acid (or phosphoric acid) is usually heated to about 80 °C. Formic acid is added slowly, drop by drop. The formation of gas should start upon addition of the first drop, otherwise the temperature should be increased.

The generated gas contains various impurities, which can be removed using gas washing bottles. Usually, the gas is passed first through $\ce{KOH}$ solution; however, you should take care to prevent any backflow of $\ce{KOH}$ solution to the sulfuric acid.