Welding Fume Control

Q: What is natural ventilation?
A: Natural ventilation is the movement of air through the workplace caused by natural forces. Outside, this is usually the wind. Inside, this may be the flow of air through open windows and doors.
 
Q: What is mechanical ventilation?
A: Mechanical ventilation is the movement of air through the workplace caused by an electrical device such as a portable fan or permanently mounted fan in the ceiling or wall.
 
Q: What is local exhaust?
A: Local exhaust is a mechanical device used to capture welding fume at or near the arc and remove contaminants from the air.
 
Q: What factors need to be considered when determining the exhaust requirements for your application?
A: The ventilation or exhaust needed for your application depends upon factors such as:

Workspace volumeWorkspace configurationNumber of weldersWelding process and currentConsumables used (mild steel, hardfacing, stainless, etc.)Allowable levels (TLV, PEL, etc.)Material welded (including paint or plating)Natural airflow 
Q: Name several types of local exhaust that can be used to control exposure to welding fume?
A: Local exhaust of welding fumes can be provided by any of the following: adjustable "elephant trunk" exhaust systems, fume extraction guns or fixed enclosures, or booths with exhaust hoods. 
 
Q: Which system is more effective and economical: general ventilation or local exhaust systems?
A: Local exhaust systems are more effective and economical to operate than a general ventilation system, particularly in the winter, because they require less replacement air to be brought into the room and heated.
 
Q: What is the minimum air velocity (speed) required near the welding arc? 
A: Minimum required air velocity at the welding arc is 100 fpm.
 
Q: When should an employee's exposure to welding fume be obtained?
A: Exposure should be checked when new ventilation equipment is installed, when the process is modified or when the welder feels uncomfortable. Periodically, exposure should be re-checked to be sure it is still working properly and is adequate.