What's in the air outside your home in the Central Valley doesn't stay outside. Agricultural dust and wildfire smoke season both affect what you're breathing indoors, and your HVAC system plays a direct role in filtering it.
Exeter sits in an agricultural region, which means dust load is a bigger year-round factor than it is in a lot of cities. Add wildfire smoke season on top of that, and the air your HVAC system pulls in and filters has more to deal with than most systems were designed for.
It depends on your current filter and system setup. A higher-rated filter can help with smoke particles, though very high-efficiency filters aren't compatible with every system — worth having someone check what your specific unit can handle.
Homes in agricultural areas often need filter changes more frequently than the standard recommendation, since dust load is higher. A technician can suggest a realistic schedule based on your specific system and location.
It depends on how long it's been since your ducts were last cleaned or inspected, especially in older homes. It's worth an assessment rather than guessing.