Meaning
Localized ventilation hardware captures airborne contaminants at the immediate point of generation before pollutants disperse into surrounding workspace air. Installing spot extraction ducting establishes a physical collection network designed to maintain indoor air quality near hazardous processes. The term ceases to apply to general facility HVAC systems or ambient air filtration units.
Capture Efficiency
Hood geometry and exhaust fan capacity determine how effectively dust or chemical fumes enter the capture duct. Designing spot extraction ducting requires matching capture velocity to contaminant generation speed to ensure complete removal. Flexible extraction arms position capture hoods close to welding or soldering joints.
Static pressure losses increase as duct length and bend count expand. High capture velocities prevent dust and chemical fumes from escaping into breathing zones, protecting operators while minimizing required air exchange volumes across the wider plant.
Airflow Resistance
Internal wall friction and sharp elbows reduce volumetric airflow through narrow capture lines. Evaluating spot extraction ducting performance involves measuring differential pressure drops across filter banks and exhaust runs. Smooth interior duct surfaces optimize air movement efficiency.
Duct diameter choices balance transport velocity against fan power demand.
Velocity Threshold
Minimum duct transport velocities prevent particulate settling and duct clogging during continuous operation. When spot extraction ducting airflow falls below required transport thresholds, particulates accumulate inside duct runs, creating fire hazards or flow blockages. Fan performance curves establish the ultimate operating boundary for extraction systems.
