Laboratory Hood: Fume Hood Types and Selection Guide

Laboratory Hood Overview

Laboratory hoods are essential containment devices that protect personnel from hazardous vapors, particulates, and biological agents. Understanding the different types of laboratory hoods ensures proper selection for specific applications and safety requirements.

Types of Laboratory Hoods

Fume Hoods (Chemical Hoods)

Standard Fume Hood

Purpose: Chemical vapor protection

Protection: Personnel only

Airflow:
- Face velocity: 80-120 fpm
- Exhaust volume: 150-300 CFM/linear ft
- 100% exhaust (ducted)

Applications:
- Chemical handling
- Solvent operations
- Acid work
- General chemistry

Ductless Fume Hood

Protection: Personnel from non-toxic vapors

Features:
- Carbon filter for vapor adsorption
- Air recirculates to room
- Portable, no ductwork

Filter Types:
- Organic vapors: Activated carbon
- Acid gases: Treated carbon
- Formaldehyde: Specialty media

Limitations:
- Not for highly toxic chemicals
- Filter capacity limited
- Regular filter replacement required

Biosafety Cabinets (Class II)

Class II Type A

Protection: Personnel + Product + Environment

Airflow:
- 70% recirculating, 30% exhaust
- HEPA filtered supply air
- Negative pressure containment

Applications:
- Biosafety Level 1-3 agents
- Cell culture work
- Pharmaceutical preparation
- Non-volatile toxic chemicals only

Class II Type B

Protection: Personnel + Product + Environment

Airflow:
- 100% exhaust (hard ducted)
- Negative pressure design
- HEPA filtered exhaust

Applications:
- Volatile chemicals (limited quantities)
- Biosafety Level 2-3
- Pharmaceutical manufacturing
- More demanding applications

Class III Biosafety Cabinet (Glove Box)

Protection: Maximum containment

Features:
- Totally enclosed
- Negative pressure throughout
- Glove ports for manipulation
- HEPA filtered supply and exhaust

Applications:
- Biosafety Level 4 agents
- Highly infectious materials
- Extreme hazard containment

Laminar Flow Hoods (Clean Benches)

Horizontal Laminar Flow

Purpose: Product protection only (NO personnel protection)

Airflow:
- HEPA filtered air flows horizontally
- Over the work surface
- Exits at front

Applications:
- Electronics assembly
- Non-hazardous sample preparation
- Aseptic dispensing
- Museum conservation

WARNING: Not for biohazardous materials!

Vertical Laminar Flow

Airflow:
- HEPA filtered air flows vertically
- Down onto work surface
- Drains at bottom

Advantages:
- Better user protection (partial)
- Better containment of spills
- Better for taller items

Applications:
- Electronics
- Optical components
- Pharmaceuticals (non-toxic)

Selection Criteria

Risk Assessment

Factors to Consider

1. Hazard Assessment
   - Chemical? Biological? Radioactive?
   - Volatility and toxicity
   - Quantity to be used

2. Performance Requirements
   - Airflow volume and velocity
   - Containment capability
   - Filter efficiency

3. Installation Constraints
   - Ductwork availability
   - Space requirements
   - Service connections

4. Operational Requirements
   - Throughput needs
   - Maintenance access
   - Energy consumption

Installation Requirements

Location

Optimal Placement:
- Away from doors and walkways
- Away from supply air vents
- Minimum 3 feet from windows
- Adequate clearance for maintenance
- Accessible to exhaust ductwork

Utilities

Required Services:
- Electrical (dedicated circuit)
- Exhaust ductwork (fume hood)
- Gas (if needed)
- Water (for eye wash nearby)

Clearance Requirements:
- Sides: 6 inches minimum
- Back: 6 inches minimum
- Top: Access for maintenance
- Front: Sash clearance

Maintenance and Testing

Certification Requirements

Initial Certification:
- After installation
- Before first use
- By qualified technician

Recertification:
- Annually
- After relocation
- After major repair
- Filter replacement

Tests Performed:
- Airflow measurement
- Smoke pattern test
- Filter integrity test (HEPA)
- Leak testing

Regular Maintenance

Daily:
- Clean work surface
- Check airflow indicator
- Verify sash operation

Monthly:
- Clean interior surfaces
- Check light operation
- Verify报警 systems

Annual:
- Professional certification
- Filter replacement (if needed)
- Full performance testing

Conclusion

Laboratory hoods are critical safety equipment requiring careful selection based on hazard assessment. Proper installation, certification, and maintenance ensure reliable protection for laboratory personnel and samples.