It is even fair to say that if a contact cleaning company spent all day, if the ductwork was completely exposed and if the ductwork was small
enough, a contact cleaning company could technically perform a thorough job if the technician was motivated to perform a thorough job. The contact cleaning method of air duct cleaning is very limited in what dirt, dust and debris is actually pulled out of a ventilation and or HVAC system. 2” diameter vacuum hoses cannot suck up 3” diameter beer cans or soda pop cans. Due to the laws of physics in that a 2” diameter vacuum hose leaves behind
all large diameter items, no airflow improvement is ever realized after the service is performed. Clumsy shop vac hoses usually cannot effectively clean through most furnaces burners, hence the ash, dirt, carbon and dust that can be found in these burners typically stay in the burners. This results in no efficiency improvement when cleaning out the burners, because the shop vac hose could not fit inside of the burners to properly clean it as compressed air or nitrogen can. Most ventilation and or HVAC systems have portions of ductwork that is not easily accessible due to portions of the ductwork being drywall finished around. Should this be the case at any given jobsite, a consumer and or customer must realize that a large portion of ductwork will not be cleaned as a result when the contact cleaning method of air duct cleaning is employed. Typically a shop vac hose can only reach up to 15’ before the hose just curls up. Some trunk lines may stretch out to over 100’ in distance, which means 15’ would be cleaned and 85’ would go untouched. 90 degree turns will almost always make the shop vac end its descent in cleaning down a pipe because the shop vac hose cannot be turned without physical intervention.