A purifier and evaporative humidifier in one 52 cm unit: 300 m³/h CADR, 650 ml/h of humidifying and a 3.2 L tank.
Updated
- 300 m³/h Clean air delivery rate (CADR)
- 16.5 dB(A) Noise at lowest setting
- 12 months Filter life (maker's estimate)
- 78 m² Recommended room size
Pros
- 300 m³/h CADR (GB/T 18801-2022) plus 650 ml/h evaporative humidifying
- 3.2 L tank, with a light that shows when it needs refilling
- Target humidity set in the Air+ app; default is 50% RH
- FY3400 filter has a carbon layer for odours and gases
- One button switches all lights off for sleeping
Cons
- Two consumables: FY3400 filter yearly and FY3401 wick every six months
- Philips asks for weekly tank and wick cleaning, with descaling soaks
- Cold tap water only, with nothing added to the tank
- Stops running if the filter alert is ignored, until a new filter is reset
- Best for
- Dry, centrally heated bedrooms or living rooms in winter that also need particle filtering.
- Not for
- Damp homes with condensation: it adds moisture, so a dehumidifier suits them better.
Our verdict
The PureProtect Water 3400 (AC3420/10) puts a humidifier inside a mid-sized Philips purifier. Philips states a 300 m³/h CADR to GB/T 18801-2022, about 25 m² at five air changes an hour on our rule (its own 78 m² figure uses NRCC-54013), and up to 650 ml of water an hour from a 3.2 L tank, tested from 23°C and 30% relative humidity.
Humidifying is evaporative: a wick, the FY3401, sits in the tank and the fan pushes air through it, so you won’t see any mist. It stops humidifying at the target, 50% RH unless you change it in the Air+ app, and a light on the front shows when the tank needs refilling or isn’t seated. PM2.5 sensing, auto and sleep modes and a lights-off button complete it.
It suits dry, centrally heated rooms in winter. If your home has condensation or mould it is the wrong machine, because it adds moisture; read air purifier or dehumidifier for mould first.
Living with it
Moisture brings upkeep. Philips asks you to wash the tank with a little mild washing-up liquid every week, clean the wick, and descale the wick with a one-hour soak in citric acid or diluted white vinegar, rinsing it gently without wringing it. Use only cold tap water, with no fragrance or other additives, and empty the tank when the unit isn’t in use. White deposits on the wick are scale and cut humidifying; yellowing is normal for the material.
Filters and running costs
There are two consumables. The FY3400 purification filter, with a pre-filter, a HEPA NanoProtect layer and carbon, lasts up to a year and isn’t washable. The FY3401 wick wants replacing about every six months, and at least once a year. Ignore the filter alert and the unit locks until a new FY3400 is fitted and reset. At its 43 W maximum, eight hours uses about 0.34 kWh. Our filter finder lists both parts.
Philips PureProtect Water 3400 Series 2-in-1 Purifier and Humidifier (AC3420/10) specs
- 300 m³/h Clean air delivery rate (CADR)
- 16.5 dB(A) Noise at lowest setting
- 12 months Filter life (maker's estimate)
- 78 m² Recommended room size
Heating, cooling, humidity
| Dehumidifying | not listed |
|---|---|
| Water tank | 3.2 L |
Cleaning
| Main filter | HEPA-type (class not stated) |
|---|---|
| Clean air delivery rate (CADR) | 300 m³/h |
| Recommended room size | 78 m² |
| Activated carbon (odours, gases) | Yes |
Noise and power
| Noise at lowest setting | 16.5 dB(A) |
|---|---|
| Power on lowest setting | not listed |
| Power at top speed | 43 W |
| Noise at top speed | 51 dB(A) |
| Standby power | not listed |
Filters
| Filter life (maker's estimate) | 12 months |
|---|---|
| Replacement filter | FY3400/30 |
Controls
| Air-quality sensor | Particle (PM2.5) |
|---|---|
| Auto mode | Yes |
| App control | Yes |
| Ioniser | None |
Size
| Height | 52 cm |
|---|---|
| Weight | 6.5 kg |
Warranty
| Warranty | 2 years |
|---|
Manufacturer figures, checked 2 Nov 2026. — means not listed.
Where to buy the Philips PureProtect Water 3400 Series 2-in-1 Purifier and Humidifier (AC3420/10)
- Philips£329.99Go to Philips (opens in a new tab)
Prices and stock change; the retailer’s page is always the final word.
Philips PureProtect Water 3400 Series 2-in-1 Purifier and Humidifier (AC3420/10) questions
How often should I change the wick on the Philips AC3420?
About every six months. The FY3401 humidification filter can last longer if it is still in good condition, but Philips says to replace it at least once a year and to use only the original part. The FY3400 purification filter is separate and lasts up to a year, so a year of use typically means two wicks and one filter.
How do I descale the Philips 2-in-1 humidification filter?
Soak it for an hour, then rinse it. Philips gives two mixes: 24 g of citric acid in 4 litres of water, or 100 ml of 6% white vinegar in 4 litres. Rinse the wick gently under a tap without squeezing or wringing it, and never put it in a washing machine or dishwasher, where it will lose its shape.
Why can't I see any mist from the Philips AC3420?
Because there isn’t meant to be any. The AC3420 humidifies by evaporation: air passes through a wet wick and carries the moisture out as invisible water vapour. To help the room reach its target humidity, keep doors and windows closed while it runs. If humidifying seems weak, check the wick for white scale and descale it.
What does the orange water light mean on the Philips AC3420?
A steady orange light means the tank needs refilling, and a blinking orange light means the tank isn’t seated properly. White means it is humidifying, and no light means the room has reached the target humidity, which is 50% RH unless you change it. You can set a different target in the Air+ app.
What water should I put in the Philips AC3420 tank?
Cold tap water only. Philips says not to use ground water or hot water, not to add fragrance or anything else, and not to pour water in from the top of the unit. Empty the tank when you aren’t using it, and clean the tank and wick, letting the wick dry, before storing it for a long time.