What does an air quality assessment actually measure?

Fine particles (PM2.5), carbon dioxide as a marker of ventilation, VOCs, nitrogen dioxide from gas appliances, humidity and temperature, room by room on calibrated instruments. We also measure the HVAC system itself: airflow, static pressure and filter condition.

What is a normal PM2.5 reading inside a Los Angeles home?

The EPA's 2024 annual standard is 9 micrograms per cubic meter and the WHO's 24-hour guideline is 15. Homes we measure in Los Angeles commonly land between 8 and 25 depending on filtration, cooking and what the outdoor air is doing that week.

Is a high CO2 reading in a bedroom dangerous?

At the levels found in homes, carbon dioxide is a signal rather than a hazard. It tells you how well the room exchanges air. Bedrooms with the door closed often climb past 1,200 parts per million overnight, and we treat 800 as the point where ventilation needs attention.

Do I need an air purifier or a fix at the system?

A portable purifier cleans the room it is standing in, which is useful and also the limit of it. Filtration and ventilation at the HVAC system treat the whole house, which is why we measure first and then decide where the fix belongs.

What's Actually in the Air Inside Los Angeles Homes

You cannot see PM2.5. You cannot smell CO2 building up while you sleep. VOCs from your new hardwood floors do not announce themselves. The air inside your home has a composition, and unless someone has measured it, you are guessing.

We measure it. Here is what we find.

The Six Things We Track

Every Baseline assessment covers the same six parameters. Not because they are the only things that matter, but because they are the ones that are measurable, actionable, and consistently present in residential environments.

PM2.5. Fine particles 2.5 microns and smaller. For scale, a human hair is about 70 microns. PM2.5 passes through most furnace filters, stays suspended for hours, and penetrates deep lung tissue. The EPA set its annual standard at 9 micrograms per cubic meter in 2024. Most LA homes we test land between 8 and 25.

CO2. Your body produces it. Your home accumulates it. In a well-ventilated house, CO2 stays below 600 ppm. In a sealed bedroom with the door closed, it can climb past 1,500 ppm overnight. At that level, research shows measurable effects on decision-making and sleep quality. We flag anything above 800 ppm.

VOCs. These are gases released by building materials, furniture, cleaning products, and personal care items. New construction homes and recently renovated spaces produce the highest readings. The complication with VOCs is that there is no single number that means "safe." We track them relative to the home's ventilation rate and look for sustained elevation.

Humidity. Target range: 40 to 60% RH. Below 30%, which is common in Los Angeles during Santa Ana conditions and summer AC use, you get dry skin, irritated airways, and cracking wood. Above 60%, mold risk increases. Most LA homes swing between both extremes depending on the season.

Temperature. Less about the thermostat setting and more about distribution. A 4-degree difference between rooms means your HVAC system is not delivering air evenly.

NOx. Nitrogen oxides, the marker for combustion happening inside the envelope. Gas cooking is the usual source. A vented appliance with a compromised flue, or an attached garage, will do it too. Below 25 ppb is unremarkable. Past 100 ppb in a home with no attached garage we look hard at the gas appliances and recommend a combustion safety check.

What the Numbers Mean Together

Individual readings tell part of the story. The relationship between them tells the rest. Ventilation is the clearest example: we do not meter it directly, we read it off how CO2 behaves through the visit, and it is usually what explains the other five.

A home with a PM2.5 of 22 and a well-functioning MERV 13 filter system is a different situation than a home with a PM2.5 of 22 and a filter that has gaps around the frame. The number is the same. The fix is completely different.

Similarly, a CO2 reading of 1,400 ppm in a sealed modern home is a ventilation problem. A CO2 reading of 1,400 ppm in a 1960s ranch with single-pane windows is unusual and might indicate an occupancy issue or a combustion appliance back-drafting.

This is why we produce a Baseline Score rather than just handing over raw numbers. It is a single composite weighted across all six measurements, with particles and carbon dioxide carrying the most, so one visit can be compared against the next instead of reading six numbers in isolation.

What Surprises People

The most common reaction during an assessment is not alarm. It is surprise. Homeowners expect their newer home, or their recently renovated home, to have better air. Often it is the opposite. Tighter construction means less natural air exchange. New materials mean higher VOC loads. The home is more energy efficient and less ventilated at the same time.

The second surprise is filtration. Half the homes we assess have filter fit issues. The filter is the right rating, installed correctly, and changed on schedule. But the frame has gaps. Air bypasses the media entirely. The filter becomes decorative.

These are not expensive problems. They are measurement problems. You cannot fix what you have not quantified.

If you are curious where your home's numbers fall, our IAQ assessment measures all six parameters in about 90 minutes. It includes a scored report with recommendations. You can also start with our free IAQ guide for an overview of what these readings mean.