The term "in duct" refers to something that is located within a duct or a channel, especially in the field of HVAC (heating, ventilation, and air conditioning). There are several synonyms for this phrase that may be used interchangeably, such as "in the pipeline", "in the ductwork", "in the channel", or "in the ventilator". These terms are commonly utilized to describe the placement of various components or systems within a larger duct or ventilation system, including air filters, heating coils, or dampers. Being familiar with these synonyms can greatly aid communication and understanding within the HVAC field, facilitating better maintenance and repairs of the overall system.