Otherwise, if furnace flue is being abandoned because no longer needed, I would require the top be removed and replaced with a domed galvanized metal cap to keep insects and maybe rodents from taking up residence or using it as a nut cache - cost probably about $50-75 additional.
The creatinine levels in both urine and blood are determined and compared. Normal creatinine clearance for healthy women is 88-128 mL/min. and 97 to 137 mL/min. in males (normal levels may vary slightly between labs). Blood urea nitrogen (BUN) level is another indicator of kidney function.
The higher the rate of clearance of waste products like creatinine, the better your kidneys are functioning. Normal rates of filtering are between 90 and 139 milliliters per minute for adult males younger than 40 years, and between 80 and 125 milliliters per minute for adult females younger than 40 years.