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AprilAire

AprilAire ARN25K

Radon mitigation fan kit

  • Radon fan
  • 6 in. fan duct diameter
  • 139 W
  • AprilAire ARN25K
  • AprilAire ARN25K, photo 2 of 4
  • AprilAire ARN25K, photo 3 of 4
  • AprilAire ARN25K, photo 4 of 4

Photos: AprilAire

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  • Pipe size6 in. fan duct diameter (6.0 in. O.D. inlet and outlet); the kit's coupling is a 6x4; the manual lists 3 or 4 in. schedule 20/40 PVC for pipe mounting
  • Power draw139 W
  • Every figure checked against the specifications AprilAire publishes
  • The maker's own performance table, point by point, unranked
Tests that check it works

About this item

As AprilAire states it

  • Motor: AC, thermally protected (standard 120 V, 60 Hz)
  • Pipe size: 6 in. fan duct diameter (6.0 in. O.D. inlet and outlet); the kit's coupling is a 6x4; the manual lists 3 or 4 in. schedule 20/40 PVC for pipe mounting
  • Max airflow: 375 CFM
  • Max power: 139 W
  • Power supply: 120 V AC, 60 Hz, 1.5 A maximum; 95 to 139 W (specification sheet) or 96 to 136 W (manual); continuous duty
  • Airflow at static pressure: 375 CFM at 0.00 in w.c.; 340 at 0.20; 282 at 0.50; 238 at 0.75; 204 at 1.00; 170 at 1.25; 140 at 1.50; 108 at 1.75; 70 at 2.00
  • Outdoor use: Rated for outdoor installation
  • Warranty: 12 months from installation or 18 months from manufacture, whichever is sooner; extended to 60 months (5 years) from installation or 66 months from manufacture when installed by a professional radon mitigation contractor (ARN25F manual; the specification sheet says 5-year); ARNALM alarm 2 years from purchase

The ARN25K is AprilAire's kit built around its ARN25F radon mitigation fan, packed with the ARNALM Radon System Alarm, the ARN05M manometer and a coupling. AprilAire rates the ARN25F, a fan with a 6 inch duct diameter, at 95 to 139 W with a recommended maximum operating pressure of 2.3 inches of water column, and pitches it at most sub-slab systems with a basement or slab of 1500 to 2500 square feet.

What you get

AprilAire's model data lists the ARN25F fan, the ARNALM alarm, the ARN05M manometer and coupling(s); its specification sheet describes the kit as including a 6x4 coupling, the manometer and the ARNALM. The number of couplings is given as one on the sheet and left open on the model data. The ARNALM's own box holds the alarm, wall and pipe mount adapters, a silicone connector elbow, the battery, two adapter screws and instructions, by its manual's list. The ARN25F's manual gives the fan as 8.6 inches high and 11.75 inches across, 6.5 lbs, with a 6.0 inch outside diameter inlet and outlet. The ARN05M's measuring range and parts list are not stated by the maker.

In the box and running costs

How it works

What it does and how

The suction, the airflow and the housing, then who has checked it

How it works

In our words, from the maker's documents

A radon fan is the part of an active soil depressurization system that runs all the time. The EPA's guide describes the vent fan drawing radon gas from below the home through the suction pipes and releasing it to the outdoor air, while creating a negative pressure or vacuum under the slab. The fan has to keep running for the system to work, which is why a system also needs something that tells the household when it stops.

That is the logic of this kit: one fan and two monitors. AprilAire says the ARN25K includes the ARN25F Radon Mitigation Fan, an ARNALM Radon System Alarm, an ARN05M Manometer and coupling(s), and its specification sheet calls the kit everything you need to set up radon mitigation and monitoring in homes. The pipe, the suction pit, the sealing and the wiring are not in the kit.

Two numbers describe what a fan can do. Static pressure, in inches of water column, is how hard it pulls against the resistance of the soil and the pipe; airflow, in cubic feet per minute, is how much air it moves. AprilAire's specification sheet lists the ARN25F's typical airflow as 375 CFM at 0 inches, 340 at 0.2, 282 at 0.5, 204 at 1.0, 140 at 1.5 and 70 at 2.0 inches. Its installation manual prints the same curve in quarter-inch steps, adding 238 CFM at 0.75, 170 at 1.25 and 108 at 1.75 inches.

AprilAire publishes a recommended maximum operating pressure rather than a maximum static pressure, and its two documents give different figures: 2.3 inches of water column on the specification sheet and 2.2 inches at sea level in the manual, which says to reduce it by about 4% per 1000 feet of altitude and by a further 10% in high temperature environments, and to add suction points if a system exceeds it. The power draw differs the same way, 95 to 139 W on the sheet and 96 to 136 W in the manual, at 120 V, 60 Hz and 1.5 A maximum. A maximum static pressure for the ARN25F is not stated by the maker.

AprilAire's manual places the ARN25F between its other two radon fans: the ARN15F for general purpose use, the ARN25F where additional airflow is required, and the ARNHPF for tight soil conditions. It says one of its fans can cover up to 2000+ square feet per slab penetration depending on the material under the slab, with tighter material covering less, and recommends a small pit of 5 to 10 gallons below the slab at each suction hole.

The two monitors work differently. The ARN05M is a U-tube manometer that AprilAire says mounts to the outside of the PVC pipe and measures vacuum pressure in real time. The ARNALM is a battery powered alarm with a piezoresistive pressure sensor; AprilAire lists a sensing range of -0.1 to -20 inches of water column and says it alarms at a 90% or greater reduction from the baseline pressure it measures when it is switched on. AprilAire's sheet says plainly that the alarm does not measure radon levels, and neither does the manometer: both watch the fan's suction, not the air in the home.

What the manufacturer says

AprilAire's own statements, attributed

  • AprilAire saysAprilAire states the ARN25K Radon Mitigation Kit includes the ARN25F Radon Mitigation Fan, an ARNALM Radon System Alarm, an ARN05M Manometer and coupling(s).
  • AprilAire saysAprilAire states its fans are specifically designed for radon mitigation and run ultra-quiet, and lists the ARN25F as energy efficient, with a water-hardened motorized impeller and a housing that stays white.
  • AprilAire saysAprilAire states the ARN25F is ETL Listed for indoor or outdoor use, with a thermally protected motor, and rated for commercial and residential use.
  • AprilAire saysAprilAire states the ARN25F's seams are sealed to inhibit radon leakage (double snap sealed) and that the fan is made in the USA with U.S. and imported parts.
  • AprilAire saysAprilAire's manual states the fan conforms to UL Standard 507 and is certified to CAN/CSA C22.2 No. 113, rated for continuous duty at 3000 RPM.
  • AprilAire saysAprilAire states the ARNALM alarm's audible and visual indicators meet the ANSI/AARST soil gas mitigation standards' system monitor requirements.

These are AprilAire's own statements, attributed to it. They are not our findings, and we have not tested this product ourselves.

Independent evidence

Who checks a device like this

C-NRPP's consumer evaluation covers electronic radon monitors, not mitigation fans, so it has no result for AprilAire ARN25K. The safety listing and performance certification the maker states are under “What the manufacturer says”, and what shows whether any fan is working in your home is a radon test after it is installed.

Specifications

Specifications

Every figure as the maker states it

Compare side by side

The maker's figures

Type
Mitigation fan, inline fan kit, with alarm and U-tube manometer
Motor
AC, thermally protected (standard 120 V, 60 Hz)
Pipe size
6 in. fan duct diameter (6.0 in. O.D. inlet and outlet); the kit's coupling is a 6x4; the manual lists 3 or 4 in. schedule 20/40 PVC for pipe mounting
Max static pressure
Not stated by the manufacturer
Max airflow
375 CFM
Max power
139 W
Power supply
120 V AC, 60 Hz, 1.5 A maximum; 95 to 139 W (specification sheet) or 96 to 136 W (manual); continuous duty
Speed control
Not stated by the manufacturer
Airflow at static pressure
375 CFM at 0.00 in w.c.; 340 at 0.20; 282 at 0.50; 238 at 0.75; 204 at 1.00; 170 at 1.25; 140 at 1.50; 108 at 1.75; 70 at 2.00
Outdoor use
Rated for outdoor installation
Warranty
12 months from installation or 18 months from manufacture, whichever is sooner; extended to 60 months (5 years) from installation or 66 months from manufacture when installed by a professional radon mitigation contractor (ARN25F manual; the specification sheet says 5-year); ARNALM alarm 2 years from purchase

What is in the box

AprilAire's model data lists the ARN25F fan, the ARNALM alarm, the ARN05M manometer and coupling(s); its specification sheet describes the kit as including a 6x4 coupling, the manometer and the ARNALM. The number of couplings is given as one on the sheet and left open on the model data. The ARNALM's own box holds the alarm, wall and pipe mount adapters, a silicone connector elbow, the battery, two adapter screws and instructions, by its manual's list. The ARN25F's manual gives the fan as 8.6 inches high and 11.75 inches across, 6.5 lbs, with a 6.0 inch outside diameter inlet and outlet. The ARN05M's measuring range and parts list are not stated by the maker.

AprilAire states the warranty two ways. Its specification sheet says all its radon mitigation fans carry a 5-year warranty. Its ARN25F manual gives 12 months from installation or 18 months from manufacture, whichever is sooner, extended to 60 months (5 years) from installation or 66 months from manufacture when a professional radon mitigation contractor installs the fan, with no extension outside the continental United States and Canada. The ARNALM alarm has its own two-year warranty from the date of purchase.

What it costs to run

The main running cost is electricity: the fan runs around the clock, at 95 to 139 W by AprilAire's specification sheet or 96 to 136 W by its manual. Your utility rate sets what that costs; AprilAire's owner's folder points to a calculator on its own site for the estimate.

The alarm runs on one 3.6 V 1/2 AA battery, and AprilAire says its low battery light comes on below 3.35 V, with a chirp every five minutes. The EPA's guide says fans may last five years or more and that manufacturer warranties tend not to exceed five years. Periodic radon retests are the other recurring cost, because the monitors only show that the fan is pulling, not what the radon level is.

Airflow at each pressure

AprilAire's performance table, point by point

Static pressureAirflow
0.00 in w.c.
375 CFM
0.20 in w.c.
340 CFM
0.50 in w.c.
282 CFM
0.75 in w.c.
238 CFM
1.00 in w.c.
204 CFM
1.25 in w.c.
170 CFM
1.50 in w.c.
140 CFM
1.75 in w.c.
108 CFM
2.00 in w.c.
70 CFM

Airflow falls as the suction the system needs rises. A mitigator matches the fan to pressure measured under the slab.

Fit and setup

Who it fits, and installation

The fit, then how a system goes in

Who it fits

Good fit if, and look elsewhere if

Good fit if

  • You or your mitigator want the fan, an audible alarm and a U-tube manometer from one maker in one package.
  • Your system calls for the higher airflow AprilAire describes for the ARN25F, within its recommended maximum of 2.2 to 2.3 inches of water column.
  • The fan will sit outdoors or in an attic, which AprilAire's manual allows, and the alarm can go indoors where the household will see and hear it.
  • You are replacing an ARN25F and the system's alarm or manometer needs replacing at the same time.

Look elsewhere if

  • A diagnostic shows tight soil that needs high suction; AprilAire points to its ARNHPF for tight soil conditions.
  • You want to turn the fan up or down with a dial; AprilAire's documents describe no speed control for the ARN25F.
  • You are designing a first system yourself; the EPA recommends a qualified mitigation contractor, and AprilAire's manual ties its five-year term to professional installation.
  • The system already has a working alarm and manometer and needs only a fan; AprilAire lists the ARN25F as a model of its own.

Installation

5 steps

  1. The EPA recommends that a qualified radon mitigation contractor fix a home, and notes that many states require radon professionals to be licensed, certified or registered. AprilAire's manual says the fan is intended for use by trained, professional, certified or licensed radon mitigators, that installation work and wiring must be done by qualified persons to all applicable codes, and that all wiring must be performed by a qualified and licensed electrician.
  2. AprilAire's manual says to mount the fan vertically, plumb and level, with the outlet pointing up so condensation drains through it, joined to the pipe with flexible couplings that also serve as a disconnect for service and for vibration isolation. The fan should not touch any building surface, is not suitable for underground burial, and can go indoors or outdoors, on the pipe or on an optional mounting bracket. Outdoor wiring needs a UL Listed watertight conduit, the fan is not meant for rigid metal conduit, and the fan should not sit on the piping without power for more than 48 hours.
  3. Where the fan goes matters as much as which one. The EPA's construction guide says the fan and every positively pressurized part of the vent pipe belong outside habitable space, so a leak at the housing or a joint cannot push radon into the home, and that the fan should go in a vertical run of the vent pipe.
  4. The alarm has its own rules. AprilAire's ARNALM instructions say it is for conditioned indoor installations only, where the occupants will readily see it, and that outdoor installation voids its warranty. It mounts on 2, 3, 4 or 6 inch pipe or on a flat surface, on the suction side of the fan at least 12 inches from it, through a 9/16 inch hole; a remote wall mount can sit within 50 feet of the pipe on tubing sold separately. It calibrates itself in 20 seconds once the battery goes in with the fan running.
  5. AprilAire's manual says a system monitor, such as the ARN05M manometer or the ARNALM alarm, is required to tell the occupants when the fan fails, and that the system label supplied with the ARN05M goes where the occupants will see it. Its owner's folder says a system should have at least two monitors, a passive U-tube and an active notification monitor, and that the fan is running when the manometer's liquid levels are uneven. The EPA's guide says a post-mitigation test should be done within 30 days of installation, but no sooner than 24 hours after the system is running with the fan on, and suggests retesting at least every two years.

To find someone to design and install a system, see radon mitigation professionals, and for how a fan fits into one, how a radon fan works.

Compare

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The same three rows for each, and the one difference that matters

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Questions

Questions people ask

6 questions about the AprilAire ARN25K, answered

Asked about the ARN25K

Is the ARN25F the right size fan for my house?

Floor area is only a starting point. AprilAire pitches the ARN25F at slabs of 1500 to 2500 square feet and its smaller ARN15F at up to 1500, and its sheet adds that soil or grade type and home construction also play into fan selection. Its owner's folder says diagnostic tests are performed to determine the system design, which is the mitigator's job before a fan is chosen.

How much air does the ARN25F move?

It depends on the suction. AprilAire lists 375 CFM with no resistance, 340 at 0.2 inches of water column, 282 at 0.5, 204 at 1.0, 140 at 1.5 and 70 at 2.0, and recommends running it no higher than 2.3 inches on its specification sheet, or 2.2 inches at sea level in its manual.

Does the alarm measure radon?

No. AprilAire's specification sheet says the ARNALM does not measure radon levels; it senses the vacuum in the pipe and alarms when it falls by 90% or more from its baseline. A radon test or monitor is what tells you the level in the home.

Can the ARN25F be installed outside?

Yes, by AprilAire's account: its specification sheet says the fan is ETL Listed for indoor or outdoor use, and its manual says it can be mounted indoors or outdoors, with outdoor wiring in a UL Listed watertight conduit. The ARNALM alarm is the exception; AprilAire says it is for conditioned indoor spaces only.

What warranty does AprilAire give?

AprilAire's specification sheet says 5 years for all its radon mitigation fans. Its ARN25F manual is narrower: 12 months from installation or 18 from manufacture, extended to 5 years from installation or 66 months from manufacture when a professional radon mitigation contractor installs the fan. The ARNALM carries two years from purchase.

Do I need a professional to install it?

AprilAire writes the ARN25F for trained, certified or licensed radon mitigators, wants a licensed electrician on the wiring, and gives the five-year term in its manual only when a professional radon mitigation contractor installs the fan. The EPA likewise recommends a qualified radon mitigation contractor, and many states license, certify or register the people who do the work.

What to do next

Updated October 8, 2026