![Anyone know what this brown stuff is? Slid out the air filter and found it underneath. New apt complex, built in 2020. : r/hvacadvice Anyone know what this brown stuff is? Slid out the air filter and found it underneath. New apt complex, built in 2020. : r/hvacadvice](https://preview.redd.it/3udo9wkhqyv81.jpg?auto=webp&s=5754c0e09b4d77f53fe3f9512cf312f072d666d0)
Anyone know what this brown stuff is? Slid out the air filter and found it underneath. New apt complex, built in 2020. : r/hvacadvice
![Air Filter Icon For Environmental Health And Safety | Presentation Graphics | Presentation PowerPoint Example | Slide Templates Air Filter Icon For Environmental Health And Safety | Presentation Graphics | Presentation PowerPoint Example | Slide Templates](https://www.slideteam.net/media/catalog/product/cache/1280x720/a/i/air_filter_icon_for_environmental_health_and_safety_slide01.jpg)
Air Filter Icon For Environmental Health And Safety | Presentation Graphics | Presentation PowerPoint Example | Slide Templates
![Vm20 Carburetor Carb W/ Air Filter Round Slide Atv Motorcycle Carb - Motorcycle Carburetors & Parts - AliExpress Vm20 Carburetor Carb W/ Air Filter Round Slide Atv Motorcycle Carb - Motorcycle Carburetors & Parts - AliExpress](https://ae01.alicdn.com/kf/HTB1BhDjXIfrK1Rjy1Xdq6yemFXa7/VM20-Carburetor-Carb-W-Air-Filter-Round-Slide-ATV-Motorcycle-Carb.jpg_Q90.jpg_.webp)
Vm20 Carburetor Carb W/ Air Filter Round Slide Atv Motorcycle Carb - Motorcycle Carburetors & Parts - AliExpress
![Amazon.com: Spectre Essentials Cabin Air Filter: Premium, 50-Percent Longer Life: Fits Select 2003-2021 TOYOTA/DODGE/PONTIAC (Tacoma, Dart, Vibe), SPC-2005 : Automotive Amazon.com: Spectre Essentials Cabin Air Filter: Premium, 50-Percent Longer Life: Fits Select 2003-2021 TOYOTA/DODGE/PONTIAC (Tacoma, Dart, Vibe), SPC-2005 : Automotive](https://m.media-amazon.com/images/I/41qosJEvfaL._AC_.jpg)
Amazon.com: Spectre Essentials Cabin Air Filter: Premium, 50-Percent Longer Life: Fits Select 2003-2021 TOYOTA/DODGE/PONTIAC (Tacoma, Dart, Vibe), SPC-2005 : Automotive
![Amazon.com: TC-Motor 22mm Carburetor Air Filter For Mikuni VM22 VM22-133 Round Slide Carb For 70cc 90cc 110cc 125cc Pit Dirt Bike Go Kart ATV Quad For Honda GX120 GX160 GX200 Clone Titan Amazon.com: TC-Motor 22mm Carburetor Air Filter For Mikuni VM22 VM22-133 Round Slide Carb For 70cc 90cc 110cc 125cc Pit Dirt Bike Go Kart ATV Quad For Honda GX120 GX160 GX200 Clone Titan](https://m.media-amazon.com/images/I/51CxxJ3CiOL.jpg)
Amazon.com: TC-Motor 22mm Carburetor Air Filter For Mikuni VM22 VM22-133 Round Slide Carb For 70cc 90cc 110cc 125cc Pit Dirt Bike Go Kart ATV Quad For Honda GX120 GX160 GX200 Clone Titan
![24" X 18 Steel Return Air Filter Grille for 1" Filter - Fixed Hinged - Ceiling Recommended - HVAC Duct Cover - Flat Stamped Face - White [Outer Dimensions: 26.5 X 19.75] - - Amazon.com 24" X 18 Steel Return Air Filter Grille for 1" Filter - Fixed Hinged - Ceiling Recommended - HVAC Duct Cover - Flat Stamped Face - White [Outer Dimensions: 26.5 X 19.75] - - Amazon.com](https://m.media-amazon.com/images/I/41xy6X4c+uL._AC_SY580_.jpg)