How Ductless Containment Differs
In a ducted laboratory fume hood the hazard leaves the building. In a ductless chemical fume hood the hazard is captured in the filter, so the filter becomes the critical safety component. That shifts attention from airflow alone to which chemicals are used, how much, and how long the filter has been in service.
The Ductless Fumehood 35-DLF100 is a floor-standing recirculating unit with a carbon filter, a listed face velocity of 0.3 m/s, an 880 x 730 x 745 mm interior and a motorized front glass window.
How Recirculating Filtration Works
A filtered fume hood follows the path below. The notes also point out the features the 35-DLF100 listing names.
- 1
Draw in
A fan pulls room air through the front opening, creating an inward flow across the work area. The listed face velocity is 0.3 m/s.
- 2
Capture
Vapors generated at the work surface are swept toward the rear and the filter.
- 3
Pre-filter
Where fitted, a pre-filter stops larger particles before the main filter.
- 4
Adsorb
Activated carbon holds vapor molecules on its surface. The listing names a carbon filter for toxic fume removal.
- 5
Return
Cleaned air passes back to the room. The range page notes optional HEPA stages for particulates.
- 6
Monitor
A digital LED display shows operating status, and the range page mentions filter alarms.
Adsorption is not permanent storage. Carbon holds a finite amount of each vapor, and once it is saturated the vapor passes through, a condition called breakthrough. The product page does not state the filter capacity, airflow volume or how breakthrough is detected on this model, so those items belong in a supplier conversation.
Practical Use Cases Without Ductwork
Ductless fume hood use is strongest where a limited, well-characterized set of chemicals is handled in modest quantities. The product page names low-velocity labs, large equipment workspaces, quiet research environments and standard laboratory settings, and the cards below describe typical workflows. Where ducting is impossible, the unit can stand in as a chemical fume hood for a defined list of reagents.
Pharmaceutical labs
Weighing, sample preparation and small-volume solvent handling where the chemical list is known and documented.
Chemical labs
Routine handling of compatible organic vapors, with work logged so filter use can be tracked.
Research and teaching labs
Bench-scale procedures where a defined set of reagents is used repeatedly and risk assessments are fixed.
Rooms without ducting
Leased space, upper floors and buildings where adding a duct and exhaust fan is impractical.
The title mentions operator protection, and the same filter-based logic applies: protection holds only while the filter suits the chemicals and has remaining capacity.
Which Vapors Suit Carbon Filtration
Activated carbon does not capture all vapors equally. The table below gives typical behavior only, and the filter supplier's chemical compatibility data and the lab risk assessment decide each case.
| Vapor type | Typical carbon behavior | Consideration |
|---|---|---|
| Many organic solvent vapors of higher molecular weight | Adsorbed well | Capacity still depends on concentration and time |
| Small volatile molecules such as methanol, ammonia and formaldehyde | Adsorbed poorly by plain carbon | May need specific filter media or a ducted hood |
| Acid vapors | Plain carbon is unsuitable | Treated or specialized media are used |
| Fine particulates and powders | Not captured by carbon | A HEPA stage is needed, listed as optional on the range page |
| Unknown, mixed or highly toxic substances | Cannot be predicted | A ducted hood or a full risk assessment is the safer route |
Ductless and Ducted Hoods Compared
The choice between formats is mostly a choice about what happens to the contaminated air. The comparison below describes typical characteristics rather than one model.
| Format | Contaminated air | Typical fit | Consideration |
|---|---|---|---|
| Ducted | Exhausted outside the building | Wide or unknown chemical range, larger quantities | Needs ductwork, makeup air and building integration |
| Ductless | Filtered and returned to the room | Defined chemical list and moderate quantities | Filter selection, monitoring and replacement are central |
Typical ducted hoods are often specified at roughly 0.4 to 0.6 m/s face velocity, depending on the standard, so the 0.3 m/s listed here reflects a different design approach and should be read alongside the containment test method. Both formats sit within the wider fume hood category, and the chemicals handled usually decide between them.
Filter Life, Monitoring and Maintenance
A fume hood filter is a consumable safety component, and a short routine keeps it effective. The points below are general practice, and the manual for the unit takes priority.
- Keep a log of chemicals and quantities used, since filter life depends on the vapor load.
- Replace filters on the schedule set by the supplier and by the log, not by the appearance of the filter.
- Use gas sensors or filter alarms where available, and treat any alarm as a stop signal.
- Check airflow at the sash opening periodically against the manufacturer value.
- Handle spent filters as hazardous waste according to local rules.
- Keep the sash at the working height, and avoid blocking the rear baffles with equipment.
- Re-evaluate the chemical list whenever a new reagent is introduced.
Specifications Worth Reading Closely
A datasheet for a carbon filter fume hood describes the cabinet well and the filtration less well, so the gaps are worth noting. The figures below come from the 35-DLF100 listing, which is also summarized in its product catalog.
| Parameter | 35-DLF100 listing | Why it matters |
|---|---|---|
| Interior size | 880 x 730 x 745 mm | Determines the largest equipment that fits in the work zone |
| Exterior size | 1000 x 840 x 2150 mm | Needs floor space and ceiling clearance |
| Maximum opening | 520 mm | Largest sash opening for loading equipment |
| Face velocity | 0.3 m/s | Inward airflow at the opening |
| Filtration | Carbon filter | Capacity, media type and life are not stated on the page |
| Sash and display | Motorized front glass window, digital LED display | Automatic sash control and status readout |
| Work surface | Phenolic resin, 750 mm height | Chemical-resistant and set at a standard working height |
| Noise | Up to 60 dB | Relevant to shared rooms |
| Lighting and UV | 18 W lamp, plus UV lamps | Illumination and surface treatment of the work zone |
| Power | 400 W; 220 V 50 Hz, 220 V 60 Hz or 110 V 60 Hz | Supply options for different regions |
| Weight | 230 kg gross | Determines handling, access and floor loading |
The standard accessory list includes a 4 m PVC exhaust duct, which is unexpected for a ductless unit, and it is worth asking what it is for. The page also describes the containment as tested but does not name the test method.
Selection Mistakes to Avoid
- Choosing ductless without listing the chemicals. The chemical list decides whether carbon suits the work at all.
- Using small polar vapors or acids with plain carbon, which captures them poorly.
- Treating filter life as a calendar item. Usage and vapor load decide when it is exhausted.
- Assuming that portable means light. The 35-DLF100 is a 230 kg floor-standing unit, so it can be relocated without ductwork but not carried.
- Skipping the containment test method. A face velocity figure alone does not describe performance.
- Comparing ductless fume hood manufacturers on size and noise alone. Filter data, monitoring and service support matter more.
- Overlooking particulates. Powders need a HEPA stage in addition to carbon.
Exploring the Wider Fume Hood Range
This hood belongs to the ductless group at Lab Expo, inside a fume hood portfolio. According to the ductless fumehood range page, these units use activated carbon filtration with optional HEPA stages, microprocessor-controlled airflow, motorized sash regulation, filter alarms and UV sterilization. A portable ductless fume hood in the usual sense is therefore a relocatable, filtered cabinet that needs only a power outlet.
Within this category, a ductless fume hood for lab use is usually weighed on interior size, filter type and capacity, monitoring and alarms, noise, power supply and footprint. The complete Fumehood category lists the configurations available.