If you recently installed or unboxed your MRCOOL mini split system, you may have noticed something that raises a common question:
Your indoor unit has two slots for air freshener filters, but the system only includes one black filter in the box.
Did something get left out?
Nope. This is completely normal — and intentional.
Let’s explain why.
What Is the Black Air Freshener Filter?
The small black filter included with many MRCOOL indoor air handlers is an air freshener (deodorizing) filter.
Unlike the primary mesh filters, which capture dust, lint, and debris, the black filter is designed to:
- Help reduce household odors
- Improve overall indoor air freshness
- Provide an additional layer of air treatment
Think of it as a bonus comfort feature, not a primary filtration component.
Your mini split’s main washable mesh filters are still doing the heavy lifting when it comes to air filtration.
Why Does the Indoor Unit Have Two Filter Slots?
Many MRCOOL indoor units include two mounting positions for deodorizing filters, but only one filter is included with the system.
This design gives homeowners flexibility.
Most spaces only need one deodorizing filter to achieve the intended effect, so MRCOOL includes one to:
- Reduce unnecessary cost
- Maintain optimal airflow
- Provide the feature without requiring additional accessories
The system is engineered to operate perfectly with one filter installed.
Do I Need a Second Air Freshener Filter?
For most homes, one filter is more than enough.
However, you can install a second filter if you want additional deodorizing performance.
Some situations where adding a second filter might help include:
- Homes with pets
- Basements or areas prone to musty smells
- Workout rooms or home gyms
- High-traffic living spaces
Adding a second filter will not harm the system, but it is not required for normal operation.
Where Should the Filter Be Installed?
If you're using a single air freshener filter (which is the most common setup), install it in either of the two available slots behind the front panel.
For the best airflow coverage, we typically recommend placing it on the left-hand side when facing the indoor unit.
Installation is simple:
- Open the front cover of the indoor unit
- Remove the mesh air filters
- Insert the black air freshener filter into the designated holder
- Reinstall the mesh filters and close the panel
That's it.
Where Can I Buy a Second Filter?
If you’d like to install a second deodorizing filter, replacement and additional MRCOOL air freshener filters are available from MRCOOL DIY Direct.
Many customers choose to add a second filter if they:
- Have pets in the home
- Are installing the unit in a basement or gym
- Want additional odor control
You can find compatible filters here:
👉 Shop MRCOOL Air Freshener Filters at MRCOOLDIYDIRECT.com
Installing a second filter is optional and will not affect normal system operation, but it can provide additional odor-reducing performance for certain environments.
The Bottom Line
Your MRCOOL mini split is designed to run perfectly with just one air freshener filter installed.
The extra slot simply gives you the option to add another if you want additional odor control.
So if you opened your box and only found one black filter, don’t worry — nothing is missing.
Your system arrived exactly as it should.