Indoor air quality monitoring has moved from a niche research tool to an accessible, practical technology, yet most commercial buildings still operate without any real-time insight into what their occupants are breathing. Sensors that measure CO₂, fine particulate matter (PM2.5), volatile organic compounds, temperature, and humidity are now widely available and affordable, but the gap between deploying sensors and using their data meaningfully remains large. Engineers specify HVAC systems, owners install monitors, and dashboards light up with numbers, but all too often, no one has decided what to do when those numbers change.

This presentation provides HVAC engineers and building professionals with a practical, end-to-end framework for IAQ monitoring in commercial buildings: from understanding what to measure and why, to sensor selection, placement, and commissioning, to translating real-time data into operational decisions that protect occupant health and justify the investment to building owners.

New construction gets the attention. Green ratings, healthy building certifications, integrated MEP design, and day-one IAQ monitoring infrastructure are increasingly standard for new commercial buildings. But the vast majority of buildings that will be occupied over the next 20 to 30 years already exist. They were built without IAQ provisions, often with undersized or poorly maintained ventilation, frequently with high-emission materials, and almost universally without any means of knowing what their occupants are actually breathing.

Retrofitting an existing building for IAQ is a fundamentally different discipline from designing a new one. You cannot right-size the air handling unit. You cannot redesign the duct layout. You cannot specify low-emission materials retroactively. You work with what is there , and the first and most important tool for working with what is there is measurement.

This presentation argues that IAQ monitoring is not the last step of a retrofit, it is the first. Before any capital is committed, before any equipment is replaced, before any consultant’s recommendation is acted upon, the building’s actual IAQ performance must be measured. Monitoring transforms a retrofit project from a series of assumptions into a series of evidence-based decisions: which zones are underperforming, which parameters are the problem, whether an intervention worked, and what to prioritise next.

Most HVAC engineers know ASHRAE Standard 62.1 — the minimum ventilation standard referenced in codes worldwide. But minimum is not the same as healthy. ASHRAE Guideline 42-2023, “Enhanced Indoor Air Quality in Commercial and Institutional Buildings,” is the companion document that takes engineers beyond compliance and into genuinely better air , and yet it remains one of the least-known documents in ASHRAE’s library.

This presentation is a plain-language introduction to Guideline 42: what it is, why it was written, what it recommends and how it can be used as a practical working tool by engineers, building owners and facility managers. There are no complex calculations, not prerequisite knowledge beyond a basic familiarity with HVAC systems. The goal is simply to make G42 familiar and useful to the professionals who design and operate the buildings that people spend their lives in.

Staring from the question every occupant asks, “is the air in this building good for me?”, the session traces ASHRAE’s answer through the 4 pillars of G42: controlling pollutant sources before they enter the occupied zone, bringing in and treating outdoor air effectively, cleaning recirculated air to a higher standard, and maintain those gains through commissioning and ongoing operations. This session makes the case that ASHRAE G42 is not an academic document for researchers, it is a working engineer’s guide to buildings that are genuinely good for the people inside them.

For decades, the industry has operated as if health and energy efficiency were competing priorities, a zero sum trade off where more ventilation means more energy, tighter envelopes mean stuffier air and the pursuit of a green rating comes at the expense of the people inside. This assumptions in both economically indefensible and technically wrong. Yet it persists, embedded in how we design, certify and operate commercial buildings.

This presentation challenges that assumption at its root and argues that the health vs energy dilemma is not a design problem. We have spent years measuring energy with extraordinary precision and occupant health not at all. When you only measure one side of the equation, you optimize for only one side. The result is the buildings that look efficient on paper but quietly undermine the performance, health and wellbeing of the people who work in them every day.