Laboratory Fume Hood: Selection, Installation, and Safety Guide

Laboratory Fume Hood Guide

A laboratory fume hood is essential safety equipment that protects laboratory personnel from hazardous vapors, gases, and dusts by containing and exhausting harmful substances. Proper selection and use of fume hoods is critical for laboratory safety.

Types of Laboratory Fume Hoods

Ducted Fume Hoods (Conventional Ventilated)

Construction:
- Exhausts air to exterior via ductwork
- Constant or variable air volume
- Most common in research labs

Advantages:
- Excellent containment
- Wide chemical compatibility
- No filter replacement concerns

Considerations:
- Requires ductwork installation
- Higher installation cost
- Energy intensive

Ductless Fume Hoods (Recirculating Carbon Filter)

Construction:
- Carbon filter removes contaminants
- Filtered air recirculates to lab
- Portable and flexible

Advantages:
- Easy installation
- No ductwork needed
- Portable
- Lower operating cost

Limitations:
- Limited filter capacity
- Not for all chemicals
- Regular filter replacement required

Perchloric Acid Fume Hoods

Special Design:
- Stainless steel construction
- Waist-level exhaust slots
- Built-in water washdown
- Explosion-proof components

Required For:
- Perchloric acid (>70%)
- Strong oxidizers
- High-hazard procedures

Fume Hood Performance Standards

Face Velocity Requirements

Containment Testing

ASME/AIHA Standard:
- Smoke visualization test
- Tracer gas test (SF6)
- Face velocity uniformity
- Sash position testing

Acceptance Criteria:
- Capture velocity sufficient
- No backstreaming
- Adequate containment at sash opening

Fume Hood Installation Requirements

Location Selection

Ideal Location:
- Away from doors and walkways
- Away from air vents
- Away from cross-drafts
- Adequate clearance for maintenance
- Accessible to services

Minimum Clearances:
- Sides: 6 inches (150mm)
- Back: 6 inches (150mm)
- Top: 12 inches (300mm)

Ductwork Installation

Duct Sizing:
- Calculate exhaust volume required
- Size ducts for 1,500-2,000 fpm velocity
- Minimize bends and length
- Use smooth internal surfaces

Materials:
- PVC for corrosive chemicals
- Stainless steel for high temperatures
- FRP (Fiberglass Reinforced Plastic)

Fume Hood Operation Best Practices

Proper Work Practices

1. Keep Sash at Proper Height
   - Working height: 12-15 inches
   - Full sash only when not working
   
2. Keep Items Behind the Sash Plane
   - Minimum 6 inches from front
   - Do not block baffles
   
3. Minimize Blocked Area
   - Large equipment blocks airflow
   - Use raised stands when possible
   - Work in center of hood
   
4. Never Work with Sash Fully Open
   - This defeats containment purpose
   - Adjust sash height appropriately

What NOT to Do

Prohibited Practices:
- Using fume hood as storage
- Rapid arm movements in front
- Placing paper in hood (airflow disruption)
- Overloading with equipment
- Working with incompatible chemicals

Maintenance and Inspection

Daily Checks

• Verify face velocity indicator
• Check for unusual sounds or vibrations
• Ensure sash moves freely
• Verify light is working

Regular Maintenance

Weekly:
- Clean work surface
- Check for damage
- Verify airflow gauge reading

Monthly:
- Full containment test
- Clean exhaust grilles
- Check ductwork connections

Annual:
- Professional performance testing
- Calibration verification
- Ductwork inspection

Conclusion

Laboratory fume hoods are critical safety equipment requiring proper selection, installation, and operation. Following these guidelines ensures optimal protection for laboratory personnel working with hazardous substances.