Sampling rate of the solution absorption method in the determination of oil suspended in compressed air

This standard states that under isodynamic conditions, the sampling flow rate qp is equal to qm×(d/D)². (Since qm = D/20 = 200/20 = 10, substituting this value gives qp = 10×(6/200)² = 0.009 L/s?) ? ? ? ? ) On-site installation: compressed air flow rate of 8,000 cubic meters per hour, pipe diameter of 200 mm ； Sampling test apparatus: silicone tube + impact-type absorption tube (containing 50 ml of tetrachloroethylene). The sampling flow rates were controlled at 0.4 L/min and 1.2 L/min respectively, using an isodynamic sampling method. 20 L of gas was sampled, and an infrared oil detector was used to measure the amount of suspended oil in the compressed air; the values obtained were 20 mg/m3 and 6 mg/m3 respectively. So which sampling rate should be used? (I read online that in atmospheric environment monitoring, the sampling rate for impact absorption tubes should be 2.8 L/min or 1–3 L/min) ；