| HEPA filtration efficiency | True HEPA filtration rated at 99.97% efficiency for particles measuring 0.3 microns. | The 0.3-micron particle size is widely used as the most penetrating particle size for HEPA performance testing. Higher filtration efficiency helps reduce recirculation of fine dust and allergens. | Request independent test documentation, filter classification, gasket condition, and the replacement-filter part specification. |
| Airflow capacity | Select airflow according to the duct size, contamination level, hose length, and required air changes. Compare performance in CFM or m³/h at a stated static pressure. | A higher free-air rating does not always mean stronger cleaning performance once hoses, filters, and duct resistance are connected. | Check the airflow curve or tested airflow at working static pressure rather than relying only on the maximum free-air figure. |
| Static pressure capability | Choose a unit with a published static-pressure rating suitable for the connected ductwork, hose, pre-filter, and HEPA filter load. | The machine must maintain useful airflow as resistance increases during operation and as filters collect dust. | Confirm the measurement units, test method, operating point, and whether the rating is positive or negative pressure. |
| Pre-filtration system | Use a staged system with a coarse or washable pre-filter, a finer secondary filter, and the final HEPA filter. | Pre-filters capture larger debris and help extend HEPA filter life, reducing pressure loss and operating costs. | Check filter sequence, filter-surface area, replacement intervals, cleaning instructions, and availability of compatible consumables. |
| Air leakage control | Use a sealed housing with secure latches, a continuous filter gasket, and sealed hose connections. | A high-efficiency filter cannot perform as intended if contaminated air bypasses the filter through gaps or damaged seals. | Inspect the housing, gasket compression, access panels, clamps, and any available leak-test or service procedure. |
| Duct and hose compatibility | Select connection sizes and adapters that match the duct openings and hose diameters used by your service team. | Correct sizing reduces airflow losses, improves setup time, and helps prevent loose connections during cleaning. | Verify inlet and outlet diameters, adapter availability, hose flexibility, maximum recommended hose length, and grounding requirements where applicable. |
| Negative-pressure operation | For containment work, choose equipment designed to maintain negative pressure in the work zone and connect it to a suitable exhaust or containment arrangement. | Negative pressure helps prevent loosened dust from migrating into occupied areas during duct cleaning or remediation. | Confirm pressure monitoring, alarm functions, exhaust routing, enclosure compatibility, and the required site-containment procedure. |
| Electrical requirements | Choose voltage, frequency, plug type, current draw, and circuit requirements that match the locations where the machine will be used. | Electrical incompatibility can cause nuisance tripping, unsafe extensions, downtime, or equipment damage. | Review the nameplate rating, recommended circuit protection, extension-cord limits, and applicable electrical-safety certification. |
| Noise level | Compare sound pressure or sound power ratings measured under the same test conditions; lower dB values are preferable for occupied buildings. | Lower operating noise can improve worker comfort and reduce disruption in offices, schools, healthcare facilities, and retail spaces. | Check the measurement distance, operating mode, filter condition, and whether hearing protection is recommended. |
| Portability and handling | Prioritize balanced handles, lockable casters, suitable machine weight, compact dimensions, and safe stair or vehicle loading arrangements. | Duct-cleaning crews often move equipment through narrow corridors, service areas, and multiple floors. | Measure doorways and storage space, check wheel durability, and assess whether two-person lifting or ramps are required. |
| Filter monitoring and maintenance | Prefer differential-pressure indicators, filter-change alerts, tool-free access where practical, and documented inspection procedures. | Monitoring helps identify clogged filters, reduced airflow, and maintenance needs before performance becomes unacceptable. | Confirm alarm thresholds, reset procedures, inspection frequency, safe filter removal, and disposal requirements for contaminated filters. |
| Operating cost | Evaluate energy consumption, filter replacement cost, maintenance labor, downtime, and expected service life instead of purchase price alone. | Consumables and labor can represent a significant portion of the total cost of ownership for frequently used equipment. | Request a maintenance schedule, consumable pricing, warranty terms, repair support, and expected replacement-part lead times. |
| Safety and compliance | Select equipment with documented electrical safety compliance and use procedures appropriate to the dust, mold, asbestos, or other contaminants encountered. | The machine, filter, containment method, and work practices must be suitable for the specific hazard; HEPA filtration alone does not make equipment appropriate for every hazardous material. | Review the safety manual, intended-use limitations, grounding instructions, hazardous-material requirements, local regulations, and worker-protection procedures. |