Cleaning efficiency of a cotton cleaning machine is calculated as the percentage of trash removed from the total trash content in the cotton feed, with 70% efficiency achieved if 800kg of trash at 4% of the total weight was reduced to 2.8% or 560kg of trash removed. Key parameters to consider for blow room machines include the number and types of machines, beater settings, production rates, fiber properties, flock sizes, grid types and positions, and environmental conditions.