How Can Businesses Improve Indoor Air Quality in Commercial Buildings?

Ask most building teams how they improve indoor air quality in commercial buildings and you get the same three answers: change the filters, add a few plants, maybe buy some air purifiers. None of that is wrong exactly. It's just that none of it starts with the question that matters, which is what the air in your building is actually doing right now. Almost nobody can answer that, and that's the real problem.

So let's go a level deeper than the usual checklist.

Start with CO2, because it tells you more than it looks like it does

Carbon dioxide isn't the pollutant you're worried about at office concentrations. It's useful for a different reason: it's the cheapest, most reliable proxy you have for whether your ventilation is keeping up with how many people are actually in the room.

Here's the logic. ASHRAE's guidance notes that in a typical office, a steady CO2 level of roughly 700 ppm above outdoor air indicates you're getting about 15 cfm of outdoor air per person, which is the rate that keeps most people from noticing stuffiness. Outdoor CO2 sits around 400 to 500 ppm. So an indoor reading in the 1,000 to 1,200 ppm range tells you ventilation is roughly where it should be. Above that, it isn't.

And this matters beyond comfort. Harvard research on cognitive function found measurable declines in decision making performance once indoor CO2 passes 1,000 ppm. A conference room that reads 1,600 ppm by the end of a long meeting isn't just stuffy. It's quietly making that meeting worse.

The practical move: put a CO2 sensor in your three worst spaces, usually the largest conference room, the densest open floor plate, and whichever corner people complain about. Log readings across a full working day, not a spot check at 11am. The shape of the curve tells you more than any single number.

Your fresh air damper is probably doing less than you think

This is the finding that surprises people. Air handling units are designed with an outdoor air intake, and that damper position is often set once at commissioning and then quietly adjusted down over the years, usually to save on cooling load. Nobody documents it. The system still runs, the office still feels cold, and the air is being recirculated far more than the original design intended.

If CO2 climbs steadily through the day and doesn't reset, that's your signal. Have the actual outdoor air volume measured rather than assumed. A certified air balancing check against the design specification is a one time exercise that often explains years of complaints.

Demand controlled ventilation is the smarter long term fix: CO2 sensors drive the damper open when occupancy rises and close it when the floor empties. You get ventilation when you need it without paying to condition outdoor air at 7pm on a Friday.

In Indian cities, more outdoor air isn't automatically better

Most indoor air quality advice online is written for climates where outdoor air is cleaner than indoor air. In Mumbai, Delhi or Pune through the winter months, that assumption breaks. Pulling in unfiltered outdoor air to fix a CO2 problem can hand you a particulate problem instead.

This is where filter specification matters more than filter frequency. ASHRAE treats MERV 8 as a baseline for commercial use, but MERV 8 does very little for fine particulates. MERV 13 is the practical floor if PM2.5 is a real concern in your location, which in most Indian metros it is. Check what's physically installed in your AHUs rather than what the AMC paperwork says, the two differ more often than you'd expect.

One more thing nobody mentions: filter differential pressure. A loaded filter restricts airflow, which quietly reduces your air changes even though the filter is technically still in place. Monitoring pressure drop tells you when to change filters based on actual loading, not a calendar date.

Humidity is the variable everyone skips

Keep relative humidity roughly between 40 and 60 percent. Below that and you get respiratory irritation and static. Above it and you're creating conditions for mold and dust mites, which is a particular risk in coastal cities through and after the monsoon. Humidity is also the hidden link between air quality and pest activity, damp conditions attract problems that get treated as separate issues entirely.

Then control what's generating the pollution

Source control does more than filtration ever will. New furniture and carpeting off gas VOCs for weeks, so air out new installations before occupancy where you can. Cleaning chemicals matter: strongly scented products introduce VOCs rather than removing them. Printer and copier rooms need dedicated exhaust, not a shared return. And pantries and waste holding areas should be exhausted directly outside rather than recirculated back into the floor.

Where to actually start

If you do only one thing: measure before you buy anything. Most buildings that install purifiers haven't established whether their problem is ventilation, filtration, humidity or a source nobody has identified, and each of those has a different fix. Two weeks of CO2, humidity and PM2.5 logging across your problem areas will tell you which conversation you're actually having.

And be a little sceptical of advice, including this, that doesn't start with data from your own building. Air quality is specific to how your building is occupied, where it sits, and how its systems were set up. Someone else's five step checklist can't know any of that.

FAQs

What is a good CO2 level for an office?

Below 1,000 ppm indicates adequate ventilation for typical office occupancy. ASHRAE guidance associates roughly 700 ppm above outdoor levels with about 15 cfm of outdoor air per person. Readings consistently above 1,200 ppm suggest ventilation is not keeping pace with occupancy.

What MERV rating should a commercial building use?

MERV 8 is the common commercial baseline, but it captures little fine particulate. MERV 13 is the practical minimum where outdoor PM2.5 is a concern, which applies to most Indian metros. Confirm the installed filter matches the design specification.

How often should commercial air filters be changed?

Replace based on measured differential pressure rather than a fixed calendar interval. A loaded filter restricts airflow and reduces air changes even while technically in place. Monitoring pressure drop catches this before occupants notice.

What humidity level is best for an office building?

Between 40 and 60 percent relative humidity. Below 40 percent causes respiratory irritation and static. Above 60 percent creates conditions for mold and dust mites, a particular risk in coastal cities during and after monsoon.