If you are going to smoke DMT at the same time as you are taking irreversible MAOI be very carefull with the dosage. I have never heard of anyone smoking DMT while taking irreversible MAOI but I have heard of people taking oral reversible MAOI and then smoking and according to them you get a very long tripp (hours) with the same intensity as a normal DMT tripp which is mentally demanding. I don't think there would be any physical risks however. Smoking DMT while you take an irreversible MAOI may make the effects last even longer than that since there is barely going to be any free MAO enzymes to break down DMT molecules in your body. Instead your body will have to get rid of the DMT molecules with the help of so called CYP450 enzymes in your liver, a process that will take a lot of time. But this also depends on how much Parnate you are taking, if you are only taking a small dose maybe not all the MAO enzymes are blocked.
Also why are you taking MAOI if I may ask? If you are depressed a bad tripp might make your depression even worse.