Complete Guide to Chemical Fume Hoods
A chemical fume hood is the most important safety equipment in any lab handling volatile or toxic chemicals. This guide covers types, sizing, installation, and safety standards to help you choose the right hood.
Types of Chemical Fume Hoods
Ducted Fume Hoods
Connect to building HVAC and exhaust air outside. Handle any chemical at any concentration. The default choice for chemistry, pharmaceutical, and research labs.
Ductless Fume Hoods
Filter air through activated carbon or HEPA filters and recirculate it. Portable, no ductwork needed. Limited to chemicals their filters can capture. Best for teaching labs and QC with known chemicals.
Benchtop Fume Hoods
Compact hoods that sit on existing benches, typically 2–4 feet wide. Available ducted or ductless. Ideal for small labs or supplemental workstations.
Walk-In Fume Hoods
Floor-mounted with full-height sash openings for tall apparatus. Used for distillation, large reaction vessels, and pilot-scale work. Available 5–8 foot widths.
Acid Digestion Hoods
Polypropylene-lined hoods for perchloric acid digestion and corrosive processes. Include integrated wash-down systems to prevent dangerous perchlorate salt buildup.
Ducted vs. Ductless: Which Do You Need?
| Factor | Ducted | Ductless |
|---|---|---|
| Chemical versatility | Handles ALL chemicals | Limited to filter-compatible |
| Installation | Requires ductwork + HVAC | Plug-and-play |
| Operating cost | Higher (exhausts conditioned air) | Lower (recirculates) |
| Filter changes | None | Every 6–24 months |
| Best for | Research, pharma, chemistry | Teaching, QC, known chemicals |
| Price range | $3,000–$15,000+ | $2,000–$8,000 |
Sizing Guide
| Width | Typical Use | Interior Work Area |
|---|---|---|
| 3 ft (36") | Small preparations, single-user | ~4.5 sq ft |
| 4 ft (48") | General chemistry, teaching labs | ~6 sq ft |
| 5 ft (60") | Most common research hood size | ~7.5 sq ft |
| 6 ft (72") | Multi-user or large apparatus | ~9 sq ft |
OSHA recommends 80–120 fpm face velocity. Modern VAV hoods save 40–60% on energy vs. constant volume systems.
Installation Planning
- Ductwork: Clear path to building exterior. PVC or stainless steel depending on chemicals.
- Make-up air: Every cubic foot exhausted must be replaced to maintain hood performance.
- Location: Away from doors, high-traffic areas, and HVAC vents. Cross-drafts compromise containment.
- Work surface: Epoxy resin, phenolic resin, or stainless steel. Match to your primary chemicals.
Safety Standards
- OSHA 29 CFR 1910.1450: Requires hoods for hazardous chemicals. Mandates face velocity monitoring and annual testing.
- ANSI/ASHRAE 110: Standard containment testing method using SF6 tracer gas.
- NFPA 45: Fire protection for laboratories including hood construction and placement.
- SEFA 1: Lab fume hood performance specifications.
Need Help Choosing the Right Fume Hood?
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Chemistry hood has been protecting lab techs since 1925. We design every lab fume hood to keep hazardous fumes away from you and your lab and maximize containment.