Laminar Flow Hood Guide
Understand laminar flow hoods for serious cultivation. Learn key specifications, buying vs building considerations, and proper usage techniques.
Laminar Flow Hood Guide
A laminar flow hood provides a continuous stream of HEPA-filtered air across your workspace, creating a reliably clean environment for culture work. It's a significant investment but essential for serious cultivation and commercial operations.
How It Works
A fan pulls room air through a HEPA (High Efficiency Particulate Air) filter. The filtered air flows in parallel streams (laminar flow) across the work surface toward you. Any contaminants you introduce are immediately blown away from your work.
True HEPA filters capture 99.97% of particles 0.3 microns or larger. This includes mold spores (typically 2-20 microns) and bacteria (0.3-5 microns).
Types of Flow Hoods
| Type | Airflow Direction | Best For |
|---|---|---|
| Horizontal | Front to back | Mushroom culture work |
| Vertical | Top to bottom | Laboratory applications |
Horizontal flow is standard for mycology. You work with your arms inside the clean air stream, and any particles you shed are blown away from your plates.
Key Specifications
CFM (Cubic Feet per Minute)
Airflow velocity matters. Target 90-100 linear feet per minute (LFM) across the work surface.
| Work Area Size | Minimum CFM |
|---|---|
| 2 ft x 2 ft | 400 CFM |
| 4 ft x 2 ft | 800 CFM |
Filter Size
Larger filters mean more working area and longer filter life.
| Filter Size | Work Area | Typical Use |
|---|---|---|
| 2' x 2' | Small | Hobby to small commercial |
| 4' x 2' | Large | Commercial production |
Buying vs Building
Commercial Units
Advantages:
- Tested and certified
- Warranty and support
- Ready to use
Disadvantages:
- Expensive ($1,000-$3,000+)
- May need modification for mycology use
DIY Construction
Advantages:
- Lower cost ($300-$800)
- Customizable size
- Educational project
Disadvantages:
- Requires construction skills
- No certification
- Must verify proper function
DIY Build Essentials
If building your own, focus on these critical elements:
The Fan
Must deliver adequate CFM with enough static pressure to push air through the HEPA filter. Inline duct fans or blower wheels are common choices.
Filter Sealing
The filter must be completely sealed to the housing. Any gap allows unfiltered air to bypass the filter, compromising the entire system.
A poorly sealed filter makes the entire hood useless. Use foam gaskets, silicone, or specialized sealing methods to eliminate gaps.
Pre-Filter
Install a pre-filter before the HEPA to catch larger particles. This extends HEPA life significantly.
Using Your Flow Hood
Turn On Early
Run the hood for 10-15 minutes before working to purge the work area of contaminants.
Work Inside the Stream
Keep all work within 6-12 inches of the filter face, where air velocity is highest.
Don't Block Airflow
Avoid stacking items that obstruct the air stream. Arrange materials to allow air to flow past them.
Work Upstream
Position clean items closer to the filter, contaminated items further away. Never pass over clean items.
Maintenance
Pre-Filter
Replace or clean monthly, or when visibly dirty. A clogged pre-filter reduces airflow.
HEPA Filter
Replace when airflow drops significantly (usually every 3-5 years with regular use). HEPA filters cannot be cleaned.
Testing
Periodically verify:
- Airflow velocity with an anemometer
- Even flow across the work surface
- No dead spots or turbulence
Placement Considerations
| Factor | Recommendation |
|---|---|
| Location | Away from doors, vents, high traffic areas |
| Height | Work surface at comfortable standing or seated height |
| Exhaust | Filtered air exits toward you—keep your face out of direct airflow |
| Power | Dedicated circuit if possible |
Comparing Options
| Option | Cost | Reliability | Skill Required |
|---|---|---|---|
| Commercial hood | $1,000-3,000 | High | None |
| Quality DIY | $400-800 | High | Moderate |
| Budget DIY | $200-400 | Variable | High |
| Still air box | $30 | Technique-dependent | Low |
Begin with a still air box while saving for a flow hood. Excellent technique in a SAB beats poor technique in front of a flow hood.
Quick Reference
Purpose: Continuous clean air for culture work Key spec: HEPA filtration, 90-100 LFM airflow Cost range: $300-$3,000+ depending on source Maintenance: Pre-filter monthly, HEPA every 3-5 years Best for: Scaling up, commercial operations, high-volume work