It helps make you more comfortable during certain procedures. It is not intended to put you to sleep. You will be able to hear and respond to any requests or directions the dentist may have. The dentist will ask you to breathe normally through your nose, and within a few minutes you should start to feel the effects of the laughing gas. You may feel light-headed or a tingling in your arms and legs. Some people say their arms and legs feel heavy. Ultimately, you should feel calm and comfortable. The effects of laughing gas will wear off soon after the mask is removed.