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Quick Answer: A Balo meter or volumetric air capture hood measures HVAC air flow at the diffuser face. It gives CFM, CMH, m³/h, or L/s readings without a duct traverse. Silver Automation Instruments supports HVAC audit teams with insertion thermal mass flow meters, differential pressure transmitters, and paperless recorders.
HVAC ventilation audits fail when teams estimate airflow instead of measuring it. The Balo Meters & Hoods approach removes most guesswork because the hood captures the air stream and converts velocity or differential pressure into a volume reading. This article covers how the hoods work, where they fit in audits, and which Silver Instruments devices work alongside them.
A Balo meter is a handheld or tripod-mounted air capture hood. It has a fabric or rigid skirt, a flow grid, a pressure sensor, and a digital readout. The hood is placed over a supply diffuser or exhaust grille. Air passes through a known cross-section inside the hood. The meter calculates volume from velocity and area. Most models display CFM, CMH, m³/h, or L/s. Some store readings for later download.
HVAC balancers use these hoods on ceiling diffusers, linear grilles, return air openings, and small exhaust points. They are common in commercial buildings, hospitals, laboratories, and pharmaceutical plants. The key advantage is speed. A duct traverse can take 15 minutes per point. A capture hood takes under 2 minutes on most diffusers.
Standards require measured air volumes. ASHRAE 111 and ISO 12599 describe test methods for balancing and air flow measurement. In Singapore, SS 553 sets ventilation rates for air-conditioned buildings. In Australia, AS 1668.2 covers mechanical ventilation. Dubai Municipality requires fresh air calculations for commercial towers. A capture hood gives auditors a direct number for each diffuser. This is better than using design drawings or fan speed assumptions.
Here is the thing. Design airflow and actual airflow rarely match. Dampers drift, filters load, coils get dirty, and flexible duct sags. We have seen this on customer sites many times. A volumetric capture hood shows the real supply or exhaust volume at the terminal. This matters for indoor air quality, CO2 dilution, and negative pressure rooms. Most engineers skip this part because duct access is hard. The hood solves the access problem at the terminal.
Place the hood over the diffuser with a good seal. Wait for the reading to stabilize. The meter shows volume directly. Record the value with the diffuser tag or room number. Some hoods have a back pressure correction factor. Check the manual for the correction method. Do not squeeze the fabric skirt during reading. For variable air volume boxes, force the VAV damper to full open before you measure, or record the BAS setpoint at the same time.
In practice, a facilities team in Ho Chi Minh City reduced a floor-by-floor audit from three nights to one night. They placed the hood on each diffuser, recorded 35 values in 90 minutes, and compared them against the design schedule the next morning. The data showed six diffusers below 60 percent of design flow. That led to a duct cleaning and filter replacement job, not a fan replacement.
A capture hood gives terminal flow. Silver Automation Instruments provides the process measurement devices for the upstream side. Use a Silver Instruments insertion thermal mass flow meter for compressed air, outdoor air intake ducts, and main air handling unit supply risers. The meter outputs 4-20 mA HART and reads air velocity from 0.1 m/s to 30 m/s with plus or minus 1 percent of reading accuracy. It fits DN80 to DN300 round ducts with a ball valve insertion kit.
Use a differential pressure transmitter across bag filters, pre-filters, and cooling coils. A rising pressure drop tells you the hood readings will fall. Silver Instruments pressure transmitters cover spans from 0 to 100 Pa up to 0 to 100 bar with 0.1 percent accuracy. A 12-channel paperless recorder with 100 ms sampling accepts PT100 temperature inputs and logs air flow, temperature, and pressure during a full audit. The recorder is useful for long-term ventilation studies in hospitals and cleanrooms.
Do not send a request that says only "need air flow meter". You will get slow quotes and generic answers. Send the duct size, duct shape, air temperature, flow range, pressure, output signal, power supply, and installation access. For example: rectangular duct 600 mm by 400 mm, air flow 2000 to 6000 CMH, 25 °C, 4-20 mA HART, 24 V DC, insertion probe with flanged connection.
Email the details to Silver Automation Instruments through flow-meter.com.au. Or call Tel: +86-25-68650347. For fast quotes use Whatsapp: +86-25-52155837 or WeChat: +86 15365082610. We reply to HVAC instrumentation quotes within 24 hours on working days.
What does a Balo air capture hood measure? It measures volumetric air flow at a supply diffuser or exhaust grille. The display shows CFM, CMH, m³/h, or L/s. Some models also read temperature.
Can a capture hood replace a duct traverse? In many commercial buildings yes. But the hood is not a replacement for a full duct traverse in every case. In tight ceiling spaces or rough ductwork, use a duct traverse or an insertion thermal mass flow meter as a cross-check.
How accurate is a volumetric capture hood? Typical field accuracy is plus or minus 3 to 5 percent of reading. Seal quality, diffuser shape, and back pressure affect the result.
Which Silver Instruments products support HVAC ventilation work? Insertion thermal mass flow meters, differential pressure transmitters, and paperless recorders. They provide 4-20 mA HART outputs and long-term logging.
What details do I need for a Silver Instruments HVAC flow meter quote? Send duct size, air flow range, temperature, pressure drop, output signal, power supply, and installation type. A simple sketch helps.
