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.
Ventilation rate. How much fresh air is entering the house per hour. This is the one that ties everything together. Low ventilation means CO2 and VOCs accumulate. It means moisture from cooking and showers lingers. It means your home is recirculating what it already has.
What the Numbers Mean Together
Individual readings tell part of the story. The relationship between them tells the rest.
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. The score weights PM2.5 at 30%, CO2 at 25%, and distributes the rest across VOCs, humidity, temperature, and NOx. Most homes score between 40 and 60. The national average is about 55.
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 costs $195 and includes a scored report with recommendations. You can also start with our free IAQ guide for an overview of what these readings mean.