Movable Fume Hood
A movable fume hood, also known as a portable or ductless fume hood, is a type of laboratory safety device that protects users from hazardous fumes, vapors, and dusts. Unlike traditional ducted fume hoods that are permanently installed and vent air outside the building, movable fume hoods are self-contained and designed for flexibility and portability.
How They Work
Movable fume hoods are "ductless," meaning they don't require connection to a building's ventilation system. Instead, they operate using a built-in fan and a multi-stage filtration system:
- Air Intake: The fan pulls contaminated air from the work area, away from the user's face.
- Pre-filtration: The air first passes through a pre-filter that captures larger particles.
- Main Filtration: The air then moves through a primary filter, typically a HEPA (High-Efficiency Particulate Air) filter for solid particles and/or an activated carbon filter for chemical vapors and gases.
- Recirculation: After being filtered, the clean air is recirculated back into the laboratory environment.
This closed-loop system allows the fume hood to be placed anywhere in the lab, as it doesn't need to be near an exhaust duct.
Key Features and Applications
Movable fume hoods are popular in settings where flexibility and ease of use are a priority. Their main applications include:
- Educational Settings: They are ideal for classrooms and demonstration purposes, as they can be easily moved to different locations.
- Light-to-Medium Duty Labs: They are suitable for labs that handle small volumes of chemicals (e.g., less than 500 mL) and a limited number of chemicals (e.g., 10 or fewer).
- Temporary Workstations: They are useful for temporary projects or in labs where it is not feasible to install a permanent ducted system.
- Small or Growing Facilities: They offer scalability, allowing labs to expand quickly without extensive and costly renovations.
Advantages and Disadvantages
Advantages:
- Portability: The main benefit is their ability to be moved and shared between different workstations.
- Lower Installation Costs: They do not require expensive ductwork or major structural modifications to a building's HVAC system.
- Energy Efficiency: They can be more energy-efficient than ducted hoods because they only use energy when they are in operation and don't constantly remove conditioned air from the room.
Disadvantages:
- Limited Application: They are not suitable for all chemical applications, especially those involving highly toxic or volatile substances that cannot be effectively filtered.
- Filter Maintenance: The filters must be regularly monitored and replaced, which can be an ongoing cost and maintenance chore.
- Risk of Exposure: There is a higher risk of chemical exposure if the wrong filter is used or if the filter is not changed in time. They are not as reliable as ducted hoods for high-risk applications.
- Not for Heavy Use: They are not designed for continuous, heavy-duty use or for handling large volumes of chemicals.
