It could be as simple as a filter where the air return enters the furnace (which is primarily intended to protect the furnace components from debris, rather than purifying the air), or it could be an electronic system built into the ductwork

Some studies indicate obesity causes high serum uric acid.[ref] Other studies indicate that high uric acid levels cause an increase in obesity.[ref] In fact, some researchers theorize that humans found it advantageous to have higher uric acid levels because it promoted fat accumulation, which was helpful for survival throughout history.[ref] Interestingly, there seems to be a U-shaped curve for uric acid levels and BMI, with the lowest uric acid found in women with a BMI of 21.3 and men with a BMI of 19.1.[ref] While the complete picture isnt clear here, obesity combined with higher uric acid levels is also associated with a greater risk of high blood pressure than either condition separately.[ref] Heart problems: High uric acid levels are linked with a greater risk of heart problems and cardiovascular mortality

In homage to the indigenous people of the Americas, our collection of Native American meerschaum pipes show the grandeur of chiefs with beautifully adorned headdresses, to the simple, proud huntsman
Thus, a single waterpipe use episode involves inhalation of approximately 90,000 ml of smoke [39,40]