Plastic bags full of recyclable (or non-recyclable) items usually removed by laborers in the beginning of the sorting process. Full bags, clear OR opaque, are treated as trash, so even clean, recyclable items in plastic bags are treated as trash and cost the facilities and the City much more money.
Plastic bags, wrap, produce bags, (and many more, we call this flexible plastic packaging) can get caught in the rotating machinery, reducing sorting efficiency and/or temporarily shutting down the facility. If plastic wrap gets caught in the machinery and shuts down the facility, workers must climb onto the machinery and cut the plastic out - which is very dangerous.
"Tanglers" (ex. plastic hoses, hangers, string lights, cords, wires, etc.) pose the same problem as plastic bags/wrap. They can wrap around or jam up machinery, damage expensive machinery, and create dangerous work environments.
Dangerous material (Propane tanks, batteries, light bulbs, chemicals, mercury-containing products. needles) can cause fires, release toxic substances and cause the facility to shut down.
Diapers & other sanitary products - when put in the recycling - are a biohazard. It can dirty other recyclables, bring infectious material into the sorting facility and be passed on to the processing facility.
Food and liquids can pose a number of issues: it can attract pests and bring them into the sorting facility, dirty other perfectly good recyclables and degrade their value, and can harbor germs and bacteria that can compromise worker health.
Poles (broomsticks, mop sticks, curtain rods, pipes, etc.) may either: be pulled out in the front line, jam up and damage machinery, (if they are metal) be sorted with other metals magnetic metal sorter (which can pose problems at the metal recycling facility if there's plastic or other items attached to the metal pole), or end up being sorted out at the end of the system by optic sorters.
Small items (ex. bottle caps, container covers (smaller than 2 inches), small toys, paper clips, pencils, etc.), can either 1) jam up machinery, 2) fall out of the system and become trash or 3) accidentally be baled with a material, and cause contamination further down the recycling line.