¾-1/2” Red. Union 3/8”OD ACSM Inlet Configuration 0.1 lpm to ACSM with PM 1 passing thru aerodynamic lens 2.9 lpm to external Pump* Sheath Flow 6 lpm dry air ¼” OD OUT 1/8” NPT Rotameter Needle Valve ACSM Pivot Splitter ½” OD thin wall ss-Tubing PD-50T-24SS 1/8” OD ss-Tubing ¾-1/2-3/8” Reducing Unions Inside Shelter PM 2.5 at 3 lpm on platform ~5 mag Goose neck connection to top of cyclone 1/4” NPT 3/8” OD flex Tubing ½”OD Qty 2: ¼” to 1/8 NPT Connect. Qty 2: ½” to ¼ NPT Connector Tube-Fittings needed: ¼” OD IN *) Pump needs to be installed outside in order to reduce heat and vibration near ACSM inside

Perma Pure Nafion Dryer (ND) for ACSM Sample PD-50T-24SS Ambient Sample 3 lpm Dry sheath ~6 lpm Operating PD-50T-24SS at 3 lpm generates a pressure drop of psid or 11.2” water, delivering sample air with a dew point of -11 o C; see chart. In SEARCH it is standard to provide sheath flow at about twice the rate of the sample flow, using a heatless dryer model from Perma Pure; see next slide for details. Operating ND with Sample In and Sheath Out at approximately the same absolute pressure lessens the need for leak-tight connections, thus preventing potential twisting of the membrane tubing and damage.

¾-1/2” Red. Union 3/8”OD SEMS (DMA-CPC) Inlet Configuration # 0.36 lpm to CPC 9.6 lpm to external Pump* Sheath Flow ¼” OD IN ¼” OD OUT 1/8” NPT 1/8” Union Rotameter Needle Valve BMI Splitter ½” OD thin wall ss-Tubing PD-200T-24SS 1/8” OD ss-Tubing ¾-1/2-3/8” Reducing Unions Inside Shelter BGI for PM 1 at 10 lpm on platform ~5 mag ½” O-ring seal 1/4” NPT 3/8” OD flex Tubing ½”OD Qty 2: ¼” to 1/8 NPT Connect. Qty 2: ½” to ¼ NPT Connector Tube-Fittings needed: *) Pump needs to be installed outside in order to reduce heat and vibration near ACSM inside. # ) When not sampling ambient aerosol, the SEMS is used in combination with an atomizer to calibrate the ACSM response with 300 nm NH4NO3 particles of different concentrations. After initial set up, this calibration procedure needs to occur daily or weekly before reducing it to a quarterly schedule once in routine operation mode.

Perma Pure Nafion Dryer (ND) for SEMS Sample PD-200T-24SS Sambien Sample 10 lpm Dry sheath ~20 Lpm Operating PD-200T-24SS at 10 Lpm generates a pressure drop of psid or 9.3” water, delivering sample air with a dew point of -12 o C; see chart. In SEARCH it is standard to provide sheath flow at about twice the rate of the sample flow, using a heatless dryer model from Perma Pure; see next slide for details. Operating ND with Sample In and Sheath Out at approximately the same absolute pressure lessens the need for leak-tight connections, thus preventing potential twisting of the membrane tubing and damage.

Perma Pure Heatless Dryer (HD) HD (7 “ Dryer, 110 VAC) provides ND sheath flow at ~6 lpm for the ACSM (~20 lpm for DMA- CPC) and ambient pressure. HD dryers consist of two chambers filled with highly adsorbing molecular sieve 4A desiccant. One chamber dries the gas stream while the opposite chamber is regenerated (purged). Purge air is a small portion of dried air taken from the drying chamber, expanded to atmospheric pressure and flowing countercurrent through the regenerating (wet) chamber. Wet purge air is released from an exhaust port in the vapor state so that no drain is required. Purge air volume is controlled with an orifice housed within the unit and is vented directly into the surrounding atmosphere. HD units have been operating very reliably for the SEARCH network, consistently generating dry air with less than 10% RH at total flow rate of up to 60 lpm. Possible reasons to fail: i)desiccant needs replacing, ii)solenoid valve stops switching, iii)circuit board fails due to lightning strikes or power delivery issues.

ZA/DA System at ATL site HD (7 “ Dryer, 110 VAC) can provide <10% RH or -40 o C DP dry air of up to ~60 lpm at ambient pressure. With currently only 26 lpm used to dry the combined ACSM and SEMS (DMA-CPC) sample air flows, at least another 30 lpm can be provided before maximum capacity is reached. Running the compressor’s duty cycle consistently above 60 % will reduce the lifetime of the working components and risk the need for replacement before the end of the 2-year study. Mfg-suggested Reflux or Split Sample methods may be considered as alternative solution (see Mfg manual). Using chart from slide #2, and assuming operation of same model PD-200T-24SS at (up to) 20 lpm generates a pressure drop of psid or 18.6” water, delivering sample air with a dew point of -8 o C. ZA for ACSM and SEMS cal 6Lpm ACSM-spl 20Lpm SEMS-spl <20Lpm DMA-sheath