Finding the Right Ductless Hood

A ductless (recirculating filtered) fume hood draws contaminated air through local filtration cartridges, typically activated carbon for vapors and HEPA/ULPA for particulates, and returns cleaned air to the room. Because they do not require a dedicated duct to the outdoors, ductless hoods are attractive where building infrastructure, cost, or flexibility are constraints. However, ductless fume hoods are not appropriate for all hazards. They are generally suitable for low-to-moderate concentrations of volatile organic compounds (VOCs), nuisance-level chemical vapors, and particulate work that does not involve highly toxic, flammable, pyrophoric, radioactive, or odorous substances for which a ducted hood or specialized local exhaust is required. For acetaldehyde, cyanide compounds, perchloric acid, and other problematic substances, safety guidelines advise against ductless systems because filter media may be rapidly saturated or chemically incompatible.

Key criteria for evaluating ductless fume hoods
  • Filtration technology and media: Quality of activated carbon (type, bed depth, impregnation for acid gases), modular sorbents for specific chemical classes, and HEPA/ULPA filters for particulates. Ask for manufacturer data on sorbent capacity and breakthrough times for your chemicals of interest.
  • Monitoring and alarms: Real-time sensors for face velocity, differential pressure, and filter saturation (or indication of breakthrough) improve safety. Reliable audible/visual alarms and data logging are valuable.
  • Certification, testing, and performance data: Independent lab testing or third-party certifications demonstrating capture efficiency, filter life under realistic loads, and airflow performance.
  • Materials of construction: Chemical-resistant surfaces, easy-to-clean interiors, and corrosion-resistant frames if acids or humid conditions are anticipated.
  • Ease of maintenance and filter replacement: Modular, user-replaceable filters and clear procedures for disposal of spent filters are important operational considerations.
  • Service, support, and training: A service network for preventive maintenance, prompt filter supply, and field testing is often as important as the initial price.
  • Noise, ergonomics, and footprint: Consider the working environment—noise levels, sash design, lighting, and how it integrates into benches and workflows.
  • Compliance and facility compatibility: Verify that the use of a ductless hood meets institutional and regulatory safety requirements for your specific applications.
When getting ready to find the “best” or right ductless hood, start with hazard characterization.

Prepare a list of all chemicals, typical concentrations, quantities, and procedures. At Mystaire, we provide an application worksheet to help you think through the application and assess your main goals and objectives when buying a ductless hood. Mystaire will provide you with an assessment of suitability for a ductless hood based on the data shared in the application worksheet. They will help match the filter media to your application and estimate expected life under your laboratory and application demands.

Mystaire is here to help you determine whether carbon filtration is right for your laboratory. A ductless hood can bring many advantages to your laboratory, including greater flexibility, reduced energy-heat consumption in the winter, and air conditioning in the summer months—keeping the lab comfortable year-round while reducing energy consumption and utility costs. Contact us today for more information on our complete line of ductless fume hoods, filtered workstations, and enclosures. Make your lab greener with a Mystaire ductless solution.