Sizing an AirZone Fan: Airflow, Sound and Duct Diameter Before Anything Else
A bathroom fan is picked in a fixed order, and picking it in any other order wastes time. First comes airflow, measured in CFM, the cubic feet of air the fan moves per minute, and the figure your local code and the room set rather than the fan. Second comes sound, measured in sones, a scale of how loud the fan reads to a person standing under it. Third comes duct diameter, which is not negotiable once the framing is up. Only after those three does the light, the heater or the sensor package matter.
Seven series and what actually separates them
The series prefix on an AirZone model is the most informative part of the number, because duct size and housing depth track it almost exactly. Pick the series first and the shortlist gets small fast. All of these sit inside bathroom exhaust fans alongside the other ventilation brands in the catalog.
SE is the largest series at 15 products, covering 90 to 150 CFM at 0.7 to 1.2 sones on either 4 inch or 6 inch duct. SNP follows with nine products at 80 to 100 CFM and 0.6 to 0.8 sones on 4 inch duct, and SNPD adds seven more at a fixed 110 CFM and 0.7 sones, also on 4 inch.
SEPD is the quiet series, six products at 140 CFM and just 0.3 sones, and it requires 6 inch duct. SES is the shallow one, five products at 80 CFM and 1.1 sones on 4 inch duct.
At the top end, SED covers four products from 200 to 500 CFM at 2.0 to 4.0 sones, wanting 8 inch duct on three of them and 6 inch on the fourth. A single S series product sits at 70 CFM and 3.6 sones on 4 inch duct.
Two series are worth calling out. SEPD is the quiet one at 0.3 sones, which is close to inaudible in a finished bathroom, and it is the series to reach for over a primary bath or anywhere adjacent to a bedroom. SES is the ultra shallow one, with a housing listed at 3 and 3 quarter inches, which is what you need when the joist bay or the ceiling cavity will not take a standard body.
Reading an AirZone model number
After the series letters comes a number, then option letters. The number is the nominal airflow, and it lands on the published CFM most of the time. Two parts do not: SNPD100 is rated 110 CFM and SEPD300 is rated 290 CFM, so read the listing rather than the label when you are close to a code minimum.
The series letters come first, as in SNPD, and they set the duct size and the housing depth. The number that follows is the nominal airflow in CFM. After that the option letters do the work.
An H means a humidity sensor, as in SNP80H, and an M means a motion sensor, as in SNPD100M. MH together means both, as in SNPD100MH. An L, L2, 3L or LED marks an integral light, as in SNPD100L2, and an X marks a heater, as in SE110X. Two numbers run together, as in SNP80-100, mean the airflow is selectable between the two settings.
Those dual-number parts are useful on a job where the room size is not final. SNP50-80, SNP50H-80H, SNP80-100 and SNP80H-100H each cover two airflow settings from one unit, so the installer sets the rate on site instead of you guessing at order time.
Duct diameter is the constraint that does not move
Airflow and sound can be traded off late in a job. Duct cannot, because the run is usually in place before the fan arrives. Four inch duct covers the SNP, SNPD, SES and S series. Six inch is required by SEPD and offered on part of the SE series. The high-volume SED units want 8 inch on three of the four parts.
Undersizing the duct against the fan is the most common reason a fan tested at 110 CFM moves far less air in a finished house, and it also makes the unit louder than its sone rating suggests. If the existing run is 4 inch, the honest options are a 4 inch fan or a new duct, not a 6 inch fan with a reducer. Guidance on duct runs, elbows and roof or wall termination sits in the ventilation guides.
AirZone does not make a remote-mount unit, where the fan body sits away from the room and pulls through a length of duct. If the job needs that, it is a different product category and it lives in inline duct fans.
What pairs with what
Accessories in this range are series-specific, and the product copy states the fit explicitly. Getting this wrong means a light kit that will not mount. The table below is taken directly from the manufacturer fit statements on the listings.
SNPLEDLK is an 11 watt LED light kit and it fits the SNP and SNPD series. SQ-LED-LK is a 10 watt kit at 4100K for the SEP, SES and SQ series, while SES-LED-LK is a 4100K kit for the SES series only.
On dampers, RDF2 fits the SNP and SNPD series and RDF3-2 fits the SE series. Neither crosses over.
One rule catches people out and it is stated on the listings rather than buried in a manual: motion sensor fans cannot use light kits. If the room needs both occupancy switching and a light, order a factory combination unit rather than a motion fan plus a kit. Separate humidity and timer control for a fan circuit, where the fan itself has no sensor, comes from fan controls.
A fire radiation damper is not an optional upgrade. It closes the duct penetration automatically in a fire and is required where the fan passes through a rated ceiling assembly. Both dampers here are series-locked, so the damper decision has to be made at the same time as the fan, not afterwards. Scheduled run-on after occupancy is handled by devices in timers and time switches.
Where AirZone sits in Lumera's catalog
Thirty eight of the 47 products appear in the bathroom exhaust fan collection, which is where to compare AirZone against the other ventilation brands on one grid. The nine that do not are the light kits and the dampers, and those are reachable from this brand page.
Within that, the 26 units with no light are filed under fan only, which is the right starting point when the room already has a separate ceiling fixture.
The 10 factory combination units sit under fan and light instead. Background reading on airflow, duct runs and termination is in the ventilation guides.
Numbers that vary across the range
These are the fields that change part to part. Exhaust fans are inspected against the mechanical code and, in a rated assembly, against the fire rating too. Where that responsibility falls is set out in the installation and code disclaimer.
- Airflow. From 70 to 500 CFM. The required rate comes from the room and the code, not from what looks reasonable.
- Sound. From 0.3 to 4.0 sones, a factor of more than ten across the range. The high-volume SED units are the loud ones.
- Duct diameter. 4 inch on 19 parts, 4 or 6 inch on 12, 6 inch on eight, 8 inch on three.
- Housing depth. Read this against the joist bay. The SES series is the shallow option at 3 and 3 quarter inches.
- Sensor package. Humidity on 21 parts, motion on nine, both on two.
- Light. Integral on 10 combination units, retrofit on seven kits, and unavailable on any motion sensor fan.
- Heater. Two parts only, so a heated bath fan narrows the range to almost nothing.
- Motor. Several listings specify a two speed DC motor. Confirm on the part, because it is not uniform.
- Damper requirement. Decide this with the fan, since both dampers fit only one series each.
Airflow, duct and accessory questions on AirZone fans
How many CFM do I need for a bathroom?
The required rate is set by the local mechanical code and the room, not by the fan brand, so start there and then pick a unit that meets or exceeds it. This range covers 70 to 500 CFM, which spans a small powder room through a large commercial restroom. If you are near a code minimum, read the published CFM on the listing rather than assuming from the model number, since two parts here are rated above or below their label.
What does a sone rating actually tell me?
Sones measure how loud the fan sounds to a person in the room, and the scale is close to linear, so two sones sounds roughly twice as loud as one. Anything at or under one sone reads as quiet in a finished bathroom. The SEPD series at 0.3 sones is the quietest here, and the high-volume SED units at 2.0 to 4.0 sones are noticeably audible, which is usually acceptable in a utility space and not over a bedroom wall.
Can I put a 6 inch fan on an existing 4 inch duct?
Not without changing the duct. Reducing the duct below what the fan expects raises static pressure, cuts the delivered airflow well below the rating, and makes the unit louder than its sone figure. If the run is 4 inch and cannot be changed, stay inside the SNP, SNPD, SES or S series, which are all built for 4 inch.
Which light kit fits my fan?
It depends on the series and the kits are not interchangeable. SNPLEDLK fits SNP and SNPD fans, SQ-LED-LK fits SEP, SES and SQ fans, and SES-LED-LK is for SES only. There is also a hard exception worth repeating: a fan with a motion sensor cannot take a light kit at all, so order a factory fan-and-light unit if you need both.
Do I need a fire radiation damper?
You need one wherever the fan penetrates a fire-rated ceiling assembly, which is common in multifamily and in garages below living space. The damper seals the fan and duct automatically during a fire. Two are stocked here and each is locked to a series, RDF2 for SNP and SNPD and RDF3-2 for SE, so confirm the requirement before you settle on the fan.
What is the difference between a humidity sensor and a motion sensor model?
A humidity sensor runs the fan when moisture rises, which handles showers without anyone touching a switch and keeps running after the room is empty. A motion sensor runs the fan on occupancy, which suits a toilet room where odor rather than moisture is the issue. Twenty one parts here have humidity sensing, nine have motion, and two have both. Remember that the motion models cannot accept a light kit.
