An invoice, bill or tab is a commercial document issued by a seller to a buyer, relating to a sale transaction and indicating the products, quantities, and agreed prices for products or services the seller had provided the buyer. Payment terms are usually stated on the invoice.
When a vent is less than 10 feet high, the vent should be at least as large as the flue collar outlet.b) Vents for draft hoods or flue collars 12 inches in diameter or less should NOT be reduced more than one pipe size.
It's vented. The plumbing in your home is vented -- you can see the vent stack sticking up about 12 inches on your roof (you might have more than one.) This stack vents sewer gases up into the air and provides some pressure to equalize the system.