What things do I need to consider when Particle Monitoring in Commercial Ventilation Systems?

1.       Can a Setra particle counter be used to monitor air quality within the ductwork of an HVAC system? Describe briefly how the system would work.

          Yes. You can mount the particle counter outside the supply or return part of the system and connect the inlet probe to the inside of the duct with a Bev-A-Line-XX tubing. Connect to your BMS via BACnet or MODBUS and monitor to the general standards of ISO particle classifications. In response to monitored particle counts, increase air changes or change filters.

 

2.       How large a space can one particle counter handle?

The volume of space or size of room does not matter as much as the design of the return ductwork and how many diffusers feed a central part of the HVAC design. For example, if 10 return diffusers converge on one central return, place the particle counter there to sum all the return air from the space. This is how large spaces can be handled by a single particle counter. So it depends largely on HVAC design.

3.       Should I commission the duct mounted particle counter with the measured particle counts in the measured space?

 Yes, comparing samples taken to a known air quality standard (i.e. ISO 14644) throughout the area the return duct covers, then using that as a comparison to the unit in duct provides additional understanding of the particle load in the return.

 

4.       How frequently should I sample particles?

      Taking a one minute sample every 15 minutes will provide sufficient data for the HVAC system to respond appropriately to increases in particle levels.  For even higher response rate, increase frequency to a one minute sample every 10 minutes.

 

5.       Should I be concerned about duct vibration, and how mounting on the duct might affect the particle counter?

 Small amounts of vibration will not affect the performance of the particle counter.

 

6.       What kind of tubing should I use to go from the particle counter to the ductwork, and how long can it be?

Bev-A-Line-XX tubing is designed to resist particulate from adhering to the inside of the tubing and is FDA approved for medical/pharmaceutical use. A length of up to 6 feet can be used to connect to the particle counter.

 

7.       Will airflow velocity or high duct static pressure affect the particle readings?

 No, not if the particle counter is installed properly. If duct static pressure exceeds 4.0” WC, connect both pump inlet and pump exhaust from the particle counter to the ductwork via Bev-A-Line tubing. This will ensure pressure equilibrium during particle counting.

 

8.       Should I upgrade my MERV filter rating?

 Yes. A higher MERV rated filter will reduce the particle counts seen by the particle monitor. Upgrading from MERV-8 to MERV-13 is an optimum choice. The MERV-13 filter will likely require replacement more frequently. The use of a particle monitor will enable the lifecycle of the filter to be maximized, thereby saving money on filters and service time.

 

9.       Should I be using 100% outdoor air (OA) to improve my indoor air quality?

Generally speaking, more OA will improve indoor air quality. Consideration should be given to the tradeoffs of energy efficiency in seasonal cold climates or those with high demands for dehumidification and mechanical cooling. The use of a particle counter can help with efficient use of additional OA to improve indoor air quality. Consult the latest versions of ASHRAE 62.1 and 62.2.

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