Multi-tier aviary systems. where conveyor belts below the tiers remove the manure at regular intervals. are becoming more common in organic egg production. The area on the tiers can be included in the net area available to the hens (also referred to as usable area) when calculating maximum indoor stocking densities in organic systems within the EU. https://www.roneverhart.com/S-mores-Snack-Mix-2LB-Bag/