I live on the main floor of an apartment condo. I have been complaining about a "belching" toilet for some time... large, sometimes explosive air bubbles and for a short while after that I cannot flush the toilet. The same thing has also happened in my kitchen sink. The Condo Board finally agreed to have the whole system cleaned right out to the street. While my problem is less frequent it still occurs. They then came in to my suite and cleaned the en-suite lines. Because of all the cleaning I don't see how there can continue to be any partial blockage yet the problem persists. Could it be a blocked vent... is this a building problem. How do I properly explain this to the Condo Board... they are starting to get exasperated with me. Thanks.

Belching=bubbles=blowback from a partial blockage. Either the plumbers missed something or there's a design flaw in the drainage.
Now if it were "gurgles" you would have a vent that's blocked. Good luck, Tom