Verdict: The Dreo Air Purifier 338S is a compact smart purifier built around a 3-in-1 HEPA filter, PM2.5 display, automatic purification, filter-life tracking and app-style smart control. DREO publishes a maximum coverage figure of 856 square feet in the US and 80 square metres in the UK, but its US pages label the 115 CFM figure differently. Those numbers are manufacturer specifications, not independent room-performance tests. The 338S is easiest to recommend when you want automated monitoring and straightforward maintenance, can place it with clear airflow, and are comfortable verifying replacement-filter availability before buying.
What the Dreo 338S is
The 338S is a single-room air purifier with a cylindrical 3-in-1 HEPA filter, a real-time PM2.5 display and an RGB air-quality indicator. It can run in automatic purification mode, expose multiple manual fan settings, and track remaining filter life. A 360-degree airflow booster is intended to draw air from around the unit rather than from one narrow intake direction. The purifier also has an aroma-pad compartment, so you can add scent separately from the filtration system.
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DREO lists a brushless DC motor, four airflow modes, six fan-speed levels and a 12-hour timer. These are control options, not measurements of noise, energy use or cleaning speed. The manufacturer describes smart control, but the supplied product information does not establish a particular app name, supported voice platform or independent sensor-accuracy result.
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#1 Best Overall
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Room size and published airflow figures
DREO gives different labels and units on its regional pages. The figures should be read as the maker’s stated maximums, not as a guarantee that every room of that size will reach a particular air-change rate or pollutant level.
| Page and region | Published figure | How DREO labels it |
|---|---|---|
| US detailed product page | 115 CFM | Maximum air volume |
| US purifier series page | 115 CFM | CADR |
| US product pages | 856 sq. ft. | Maximum coverage |
| UK product page | 196 m³/h | CADR |
| UK product page | 80 m² | Maximum coverage |
The difference between “maximum air volume” and “CADR” is not merely cosmetic. Air volume describes how much air the fan moves; CADR is normally a clean-air delivery measure that also reflects filtration and test conditions. Because DREO’s US pages use both labels for 115 CFM, do not combine the number with an assumed air-change rate or compare it directly with another purifier’s independently tested CADR without checking each test method.
For a real room, use the coverage figure as an upper-bound shopping reference and then account for ceiling height, doors, open-plan connections, pollution sources and the speed you expect to run. A bedroom with the door closed is a different load from an open living area of the same floor area. If you need a guaranteed air-change target for smoke, allergens or a clinical setting, the published specifications do not establish one.
Filtration and particle monitoring
3-in-1 HEPA filter
The 338S uses a 3-in-1 HEPA filter. DREO’s compatible replacement-filter page says the HEPA layer captures 99.97% of airborne particles as small as 0.3 micrometres. That is a filter-layer claim from the manufacturer; it is not evidence here of 99.97% removal throughout a whole room, at every fan speed, or for every pollutant.
The filter must remain dry. Moisture can support mold growth, so do not wash it, rinse it or store it in a humid location. Surface dust can be removed as part of the dry cleaning procedure, but a saturated or visibly damaged filter should be replaced rather than revived with water.
PM2.5 display and RGB indicator
A PM2.5 reading gives the unit a way to show fine-particle concentration trends, while the RGB indicator provides a quick visual air-quality status. Treat the display as a convenient onboard reading rather than a certified environmental monitor. Placement, nearby cooking, open windows and the room’s air mixing can all affect what the sensor sees.
Aroma-pad compartment
The aroma compartment is separate from the filter’s cleaning job. Scent does not make the purifier remove particles more effectively, and fragrances can be unsuitable for people with sensitivities. Use only the intended aroma-pad area and keep oils away from the filter and electrical openings.
Rank #2
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Controls and day-to-day operation
- Automatic purification: lets the purifier adjust operation in response to its air-quality sensing system.
- Four airflow modes: provide distinct operating behaviors beyond the individual speed settings.
- Six fan-speed levels: let you trade airflow for a quieter or less forceful setting, although no independent decibel figures are established.
- 12-hour timer: schedules a defined operating period rather than continuous running.
- Smart control: provides remote or connected control as described by DREO; the supplied information does not specify every compatible platform.
- Filter-life tracking: estimates when service is due and displays a reminder. The reminder does not reset automatically after a filter change.
In normal use, automatic mode is the simplest starting point: let the sensor respond to changes, then use a manual speed when you need a predictable operating level. A timer is useful when you want a set run after cooking or before sleep, but a timed shutdown also means the purifier is no longer cleaning the room after the period ends.
What comes in the box
- Dreo 338S air purifier
- One filter
- Three aroma pads, with one pre-installed
- User guide
- Safety instructions
Check the filter itself before powering on. The factory filter is shipped in protective plastic and with yellow cardboard packaging that must be removed. Leaving that packaging in place blocks airflow and can make the purifier appear defective.
First-use setup
- Choose a clear location. Put the purifier on a stable, level surface with open space around the air inlet and outlet. Avoid wedging it into a corner or crowding it with furniture.
- Power off before handling the filter. Do not connect the purifier to power until the shipping materials have been removed.
- Access the filter. Remove the filter from the purifier and take off all plastic packaging and the yellow cardboard protection.
- Reinstall the dry filter. Place the unpackaged filter back in the unit and secure the cover as directed in the user guide.
- Start with automatic purification. Observe the PM2.5 display and RGB indicator while the room settles; readings can change as air mixes.
- Keep inlets and outlets open. Curtains, walls, boxes and furniture immediately beside the unit can restrict its effective airflow.
If the purifier was moved from a cold or damp environment, allow it to reach room conditions and ensure every component is dry before operation. The manufacturer specifically warns against operating with the filter packaging still installed.
How to replace the 338S filter
DREO lists a model-specific replacement filter compatible with the 338S and model designation DR-HAP008S. Confirm that the listing explicitly names your model before ordering; filter shapes and sealing surfaces are not interchangeable simply because another cartridge looks similar.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problems- Turn the purifier off and unplug it. Never open the bottom cover while the unit is powered.
- Turn the purifier upside down. Protect the top surface from scratches and keep the unit stable while you work.
- Unlock and remove the bottom cover. Follow the lock direction shown on the cover or in the user guide.
- Lift out the old filter. If it is heavily loaded, place it directly into a bag to keep dust from spreading.
- Unwrap the new filter completely. Remove its plastic packaging before installation; do not operate the purifier with the wrapping in place.
- Install the new filter and lock the cover. Check that it sits evenly and that the cover is fully secured.
- Reset the filter reminder. Reconnect power, then hold the “5s Reset Filter” button for five seconds, until the purifier beeps.
The reset is a separate step from the physical replacement. DREO’s FAQ states that the Filter Change Reminder will not reset automatically, so a new filter can still show an old service warning unless you perform the five-second reset.
Cleaning and storage
Dry-cleaning routine
- Unplug the purifier before cleaning.
- Vacuum dust from inside the unit and from the top grid.
- Use a soft, dry brush to clean the outer surface of the filter.
- Wipe the exterior with a dry, soft, non-abrasive cloth.
Do not wet the filter or put it back while damp. Do not use abrasive materials on the housing. If the unit will be stored, keep the filter and purifier in a dry environment; humidity is specifically cautioned against because it can allow mold to grow on the filter media.
When cleaning does not restore airflow
A clogged filter can restrict air movement even when the fan still runs. If dry cleaning does not help, replacement is the appropriate next maintenance step. Also check that the bottom cover is locked and that no packaging or object is blocking an inlet or outlet.
Rank #3
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Troubleshooting weak airflow or little visible improvement
Airflow feels weak
- Confirm that all shipping plastic and yellow cardboard were removed from the filter.
- Move the purifier away from walls, curtains and furniture that cover the inlet or outlet.
- Inspect the filter for heavy loading or a blockage.
- Verify that the bottom cover is correctly locked after filter service.
- Try a higher fan-speed level briefly to determine whether the issue is restricted airflow or a control setting.
The air-quality reading does not improve
- Close windows and doors while evaluating the purifier; outdoor air can continuously add particles.
- Move the unit out of a crowded area or corner so its sensor and airflow are not isolated.
- Look for an active source such as cooking, smoke, dust-generating work or a recently disturbed carpet.
- Allow time for air to mix through the room instead of judging the display immediately after changing placement.
These checks come from DREO’s troubleshooting guidance. They do not diagnose every possible electrical, sensor or motor fault. If the purifier will not power on, repeatedly reports an error or makes an abnormal mechanical sound, stop using it and follow the support instructions supplied with the unit.
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A fair comparison starts with the room, not the advertised square-foot number. Check each model’s room-specific clean-air delivery and the air-change target used to derive its coverage. A figure labeled CADR on one page may have been measured under different conditions from a figure labeled airflow or maximum air volume on another page.
Next compare independently measured noise at the speeds you will actually use, operating and standby power, and the method used to assess sensor accuracy. The 338S offers six speeds and automatic sensing, but the product information does not establish decibel, wattage or calibration results. Those omissions matter if the purifier will run beside a bed, in a nursery or continuously in a high-energy-cost area.
Finally, compare the complete ownership picture: the exact replacement-filter part number, current filter price and availability, reminder and reset procedure, cleaning requirements, app or remote-control functions, and warranty terms in your market. The 338S has a listed compatible cartridge for 338S/DR-HAP008S, but retail pricing, stock and connected-device support can change.
Ownership costs and replacement planning
No stable retail price or replacement-filter price is established in the product information, so a purchase decision should use the current listing rather than an old review figure. Before ordering, confirm that the seller identifies the unit as the 338S and that the replacement page explicitly names 338S or DR-HAP008S. Generic cartridges may fit visually while failing to seal correctly.
Recommended Free Tools
The filter-life tracker is useful for scheduling, but the supplied specifications do not promise a universal service interval. Actual service timing depends on particle load, operating hours, fan speed and room conditions. Inspect airflow and filter condition as well as the reminder. Budget for the cartridge itself and for shipping or local availability, especially if the purifier is your only unit.
Aroma pads are included in the box, with one installed, but they are optional consumables and do not improve particle filtration. Keep fragrance materials away from the filter and electrical openings, and discontinue their use if occupants are sensitive to scented products.
Rank #4
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Noise, energy use and sensor accuracy: what is not established
The product information identifies a brushless DC motor and six speed levels, but it does not provide an independently measured noise range, wattage, standby consumption or sensor-accuracy result. It would therefore be misleading to call the 338S silent, energy-efficient or laboratory-accurate based only on the listed features.
If those factors determine your purchase, look for a test that reports the measurement conditions: distance and fan speed for noise, operating mode and voltage for power, and the reference instrument and particle concentration for sensor accuracy. The available manufacturer specifications do not supply those comparisons.
Strengths and limitations for a buying decision
Reasons the 338S may fit
- Real-time PM2.5 display and RGB status make air-quality changes visible without an external monitor.
- Automatic purification, four modes, six speeds and a 12-hour timer provide more control than a single-speed unit.
- Filter-life tracking and a model-specific replacement cartridge make the maintenance process explicit.
- The 360-degree airflow design can be easier to position than a purifier that requires one large front clearance zone.
- The aroma-pad compartment and three included pads add an optional scent function without changing the filter.
Reasons to be cautious
- The US documentation labels the same 115 CFM figure as maximum air volume on one page and CADR on another.
- Coverage figures are maximum manufacturer claims, not room-specific air-change guarantees.
- No independent noise, energy, filtration, sensor or whole-room performance results are established here.
- The filter reminder requires a manual five-second reset after replacement.
- Filter packaging must be removed before first use, and the filter must stay dry throughout ownership.
Should you buy the Dreo 338S?
Choose the 338S if your priority is a smart, sensor-equipped purifier with automatic operation, visible PM2.5 feedback and a clearly defined replacement procedure. It is most defensible for a single room that can be arranged with open space around the unit and whose size is within DREO’s regional coverage claims.
Be more cautious if you need independently verified CADR, a guaranteed air-change rate, published decibel and wattage figures, or clinical-grade monitoring. In those cases, the 338S’s manufacturer specifications do not answer the key performance questions, and you should require independent measurements before treating it as a tested solution.
Before purchase, verify three practical details: the listing is the 338S rather than a similarly named model, the replacement cartridge explicitly states compatibility with 338S/DR-HAP008S, and the seller’s current price and availability meet your budget. Retail pricing, stock, warranty terms and connected-device support can change by market and date.
Frequently Asked Questions
What room size is the Dreo 338S rated for?
DREO lists maximum coverage of 856 square feet on its US product pages and 80 square metres on its UK page. The US detailed page lists 115 CFM as maximum air volume, while a US series page labels 115 CFM as CADR; the UK page lists 196 m³/h CADR. Treat these as manufacturer-published maximums, not a guaranteed air-change rate. Ceiling height, open doors, room connections and pollution sources can materially change results.
What filter does the Dreo 338S use?
It uses a cylindrical 3-in-1 HEPA filter. DREO’s compatible replacement-filter page identifies a cartridge for the 338S and model designation DR-HAP008S, with a manufacturer claim that its HEPA layer captures 99.97% of airborne particles as small as 0.3 micrometres. Confirm the model number on the listing before ordering because similar-looking filters are not automatically compatible.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
How do I replace the Dreo 338S filter?
Turn the purifier off and unplug it, turn it upside down, unlock the bottom cover and remove the old filter. Unwrap the new filter completely, install it, and lock the cover. Restore power and hold the “5s Reset Filter” button for five seconds until the unit beeps. DREO says the reminder does not reset automatically.
Can I wash or rinse the 338S filter?
No. DREO instructs owners to keep the filter dry because moisture can allow mold to grow. Vacuum the inside of the unit and top grid, brush the outer filter surface with a soft dry brush, and wipe the housing with a dry, non-abrasive cloth. Replace a heavily loaded or damp filter rather than washing it.
Why is airflow weak after setup or filter replacement?
First check that the filter’s plastic wrapping and yellow cardboard were removed. Then confirm that the bottom cover is locked, inspect the filter for clogging, and move the purifier away from walls, curtains or furniture blocking the inlet or outlet. A higher fan setting can help distinguish a control setting from a physical obstruction.
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Close windows and doors while evaluating the unit, move it out of a crowded corner, and look for active sources such as cooking, smoke, dust or disturbed carpet. Allow time for air to mix through the room. The display is an onboard reading, not a certified environmental monitor, and the available product information does not establish sensor accuracy.
Does the 338S include aroma pads?
Yes. DREO lists three aroma pads in the box, with one pre-installed, and an aroma-pad compartment in the purifier. Aroma is separate from filtration and does not improve particle removal. Keep oils away from the filter and electrical openings, and avoid fragrance if household members are sensitive.
Is the Dreo 338S quiet or energy efficient?
The product information names a brushless DC motor and six fan speeds but does not provide independent decibel, wattage or standby-consumption measurements. Do not assume silent operation or a particular running cost from the feature list. Look for tests that state fan speed, distance, voltage and measurement method if those factors are important.
What should I check before buying?
Verify that the listing is specifically for the 338S, that the replacement cartridge states compatibility with 338S/DR-HAP008S, and that current price, stock, warranty and connected-device support suit your market. These commercial details can change, and no fixed retail or filter price is established by the product specifications.
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The Bottom Line
Bottom line: The Dreo 338S offers a useful combination of PM2.5 visibility, automatic purification, multiple controls and model-specific filter support. Its 115 CFM and coverage numbers vary in labeling by region, and no independent noise, energy, sensor or whole-room performance result is established here. Buy it for the smart features and manageable maintenance, after confirming placement, replacement-filter availability and current ownership cost.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
