Pit additives on the market offer solutions for the problem of odour nuisance from pig barns. They are also intended to improve manure characteristics such as handling ease, pit gas reduction, nutrient retention ans waste strength. Most of the scientific testing in this area has been completed ina laboratory or on a bench scale. To truly evaluate the effectiveness of such products in conditions duplicating most commercial barn situations, a protocol was developed. The objective of this experiment was to evaluate the effectiveness of manure pit additives in reducing odour threshold and gas concentrations above the manure surface, in reducing solids and manure strength, and maintaining nutrient and micro-nutrient content in the manure, for commercial-scale manure pits and simulated earthen manure storages.