How do you read a VOC reading, and what does a new mattress emit?

Updated October 7, 2026.

A home VOC monitor gives you one number for a mix of many gases, and the low-cost sensors in most units cannot turn that mix into a true concentration. Lab work fills in the other half. In a University of Texas study, new crib mattresses released about four times as many VOCs as old crib mattresses (UT Austin). The same study found that mean total VOC emission rates were 56 μg/m2h at 23 °C and 139 μg/m2h at 36 °C, which is 73°F against 97°F (Boor et al., 2014).

Short answer: Treat a home monitor's VOC number as a trend, not a dose. Expect it to jump when you unwrap a mattress and then fall over the following days. In a study of two memory foam mattresses, emissions peaked on day one and the modeled 32-day averages were about 20 and 33 µg/m³ (Beckett et al., 2022). German guidance treats under 300 µg/m³ as the target (PubMed). Air the room hard in the first week and look for a label that limits emissions from the whole mattress.

This guide is for: people who have just unwrapped a mattress, own a home air monitor, and want to know whether the number it shows means anything.

Key Takeaways

Three findings that matter most when you hold a VOC reading next to a new mattress, each tied to a published figure you can check.

1. A home VOC sensor tracks change, not dose. Sensirion's VOC Index is used in many monitors. The algorithm maps the average indoor gas composition from roughly the past 24 hours to 100, and a persistent source can gradually become part of the learned background (VisiblAir).
2. New foam emits most in its first days. Two memory foam mattresses peaked on day one of a 32-day study. The modeled one-year average concentrations were 2.7 and 4.2 μg/m3 (Beckett et al., 2022), far below the 300 µg/m³ German target.
3. Heat is the driver you can plan around. Warming crib mattress foam from 73°F (23°C) to 97°F (36°C) raised its average emission rate from 56 to 139 µg/m²·h (Boor et al., 2014). That is about 2.5 times, so it pays to air a new mattress before you sleep on it.

On This Page

The nine questions this guide answers, in order, from what the number on a monitor means to when a reading should change what you do.

What does a VOC reading on a home monitor measure?

Most home monitors report one blended number from a metal-oxide sensor that reacts to many gases at once and cannot say which one it found.

VOCs are carbon-based chemicals that turn to gas at room temperature. The EPA reports that levels of several organics average 2 to 5 times higher indoors than outdoors (EPA). A home monitor tries to fold them all into one figure, sold either as TVOC (total VOCs) or as a VOC index.

The sensor in most consumer units is a small heated metal-oxide chip. Sensirion makes many of these chips, and it says its sensor cannot give an absolute concentration and cannot tell one gas from another. In its own words, the sensor cannot provide an absolute concentration (how much?) or – differently to a nose – it cannot discriminate between VOCs (which gas?) (Sensirion).

Other things move the number too. Temperature, humidity and airflow can influence the oxidation reactions on the sensor surface, and sensor baselines shift over time with no easy way to recalibrate low-cost sensors (AirGradient). If your bedroom swings between dry and damp, the reading swings with it. Our guide to the ideal humidity for a bedroom gives the range worth holding.

A lab works differently. In the University of Texas crib mattress study, the researchers placed mattress samples in a chamber and used gas chromatography-mass spectrometry to determine the rate of VOCs released (C&EN, 2014). A home reading and a lab result are different kinds of number, and much of the confusion about mattress VOCs starts when people compare the two directly.

What do ppb, mg/m³ and a VOC index number mean?

Mass units and volume units are not interchangeable, and an index of 100 means normal for your room lately, not clean air by any fixed rule.

Monitors use four common kinds of display, and the same bedroom air can look very different on each one.

Certifiers have the conversion problem too. CertiPUR-US says that its limits for VOC emissions and the results reported by laboratories are in mg/m3 units, converted to parts per million for consumer marketing. It converts using the formula (mg/m3 x 24.45) / molecular weight = ppm (CertiPUR-US Technical Guidelines, 2025).

Index devices call for a different habit. Some monitors show "ppb" from the same kind of chip, but AirGradient says a fundamentally relative sensor signal or index is converted into a number labelled as "ppb," and that it does not reflect the actual concentration of VOCs in the air and can vary widely depending on the chemical mixture present (AirGradient). Read an index as a direction, never as an amount.

What VOC level is too high for a bedroom?

German indoor air guidance sets under 300 µg/m³ as the target and treats 1,000 to 3,000 µg/m³ as a level to limit to months, not years.

The clearest scale for total VOCs comes from a German indoor air hygiene working group linked to the Umweltbundesamt, Germany's federal environment agency. It was written for lab-grade measurements.

Levels 1 to 3 come from the working group's scheme (PubMed), and level 4 describes a room usable for at most one month with increased ventilation (Springer). Levels above 10 mg/m³ are regarded as hygienically unacceptable (PMC). The 950 figure corresponds to the 95th percentile of the German Environmental Health Survey from 2014 to 2017 (Umweltbundesamt).

Two cautions apply. The levels hold only when single-substance guide values are not exceeded, so a modest total can still hide one compound that matters. Formaldehyde, one of the best known VOCs, is one of the few indoor air pollutants that can be readily measured (EPA). The second caution is your sensor. A chip that cannot report an absolute concentration cannot place your room on this scale.

What does a new mattress emit in its first month?

Foam gives off the most in the first hours and days after unwrapping, then falls steeply, though low emissions go on for weeks after the smell.

The best whole-mattress data come from a 2022 study that followed two new memory foam mattresses in a simulated consumer use environment over the course of 32 days. Airborne concentrations of 2-propanol, acetone, chloromethane, toluene, and total VOCs peaked during the first day after installation and progressively decayed over the following 31 days (Beckett et al., 2022). Those four compounds made up approximately 81% and 95% of the first-year total VOC concentration of the two mattresses, which means most of the first-month exposure lands in the first days.

The Toronto team bought 16 new infant mattresses from major North American sellers and analyzed their compositions for 45 semivolatile chemicals, and in all, 21 compounds were detected (C&EN, 2025). In the Texas work, mattresses emitted VOCs at a rate of 87.1 micrograms per square meter per hour on average, while older mattresses emitted 22.1 (UT Austin). These figures are rates per square meter of foam, not concentrations in a room.

Does body heat make a mattress give off more VOCs?

Yes. Studies that warmed mattress foam to body temperature found higher emissions, and heat mattered more than humidity or carbon dioxide.

Every study in this guide agrees that heat raises emissions. Crib mattress samples averaged 56 µg/m²·h at 73°F and 139 at 97°F (Boor et al., 2014). In the same study's room-size chamber, TVOC concentrations sampled in the breathing zone were greater than the bulk room air by factors in the range of 1.8 to 2.4.

A 2019 study of polyurethane mattresses tested the conditions around a sleeping body one at a time. Under sleeping conditions VOC emissions increased significantly, and elevated heat seemed to be the major contributor compared to elevated relative humidity and CO2 concentration (Oz et al., 2019).

The 2025 Toronto work looked at heavier chemicals. Mattresses were tested at body temperature (37.5°C / 99.5°F) and under pressure simulating a 7.5 kg (16.5 lb) infant (Earth.com). Chemical emissions increased substantially, as much as by several times (EurekAlert).

Your own warmth sets the emission rate at the surface you breathe over, so a monitor on a dresser across the room will read lower than the air at your pillow. A cool room does not switch this effect off, because the foam under you still warms from the heat your body gives off in sleep. It does keep the rest of the mattress cooler, and our guide to what temperature a bedroom should be for sleep covers the settings people find comfortable.

What do mattress emission labels limit, and what do they miss?

Foam labels test a foam sample, whole-mattress labels test the finished bed, and neither TVOC figure covers flame retardants or phthalates.

Two emission labels came up again and again on the seller pages we read, and they test different things. CertiPUR-US certified foams are tested using a small chamber test standardized by ISO, in which foam samples are conditioned for 72 hours before total VOC emissions are measured (CertiPUR-US). Formaldehyde must test below 0.1 parts per million. The program covers foam only, not the glue, the cover or the fire barrier in the finished bed.

GREENGUARD Gold, run by UL, sets criteria for furniture and mattresses as finished products. Its maximum allowable predicted concentration is 0.22 mg/m³ total VOCs and 9 µg/m³ (7.3 ppb) formaldehyde, with TVOC defined as the total response of measured VOCs in the C6 – C16 range, calibrated to a toluene surrogate (UL certification criteria). The two numbers come from different tests, a foam sample in one case and a finished mattress in the other, so they cannot be set side by side.

Neither total covers the heavier, semivolatile chemicals. One review of the program notes that the certification does not limit semi-VOCs, like phthalates, biocides, and flame retardants (My Chemical-Free House). CertiPUR-US does screen foam content for listed flame retardants, but that content screen is a separate test from its emissions figure. In the Toronto study, two certified mattresses were included, and one contained several phthalates and flame retardants (Earth.com). A low TVOC number only covers the lighter compounds.

What do mattress sellers' pages say about emissions?

We counted what nine seller and retailer pages state about emissions. Most gave a certification figure or a number of days, few gave conditions.

We read nine public mattress seller and retailer pages about off-gassing and emission certifications, found through search on September 27, 2026. We sorted what each page's emissions passage said into three buckets. We only counted what the pages said; nothing was measured, smelled or tested here.

Three of the five pages that gave a figure quoted 0.5 parts per million. None of those three said, in the passage we read, that the certifier sets its limit in mg/m³ and converts it for marketing. No page in the set gave a measured concentration for the mattress it was selling.

That gap matters when you compare what a page says with what your monitor shows. A certification figure is a pass mark for a test sample, not a reading from your bed, and none of the passages we read said so. When a page gives only a number of days, it is describing how long the smell lasts. The emissions themselves can go on for longer.

How do you check a new mattress with a VOC monitor?

Take a baseline in the empty room first, unwrap with a window open, and read the trend over several days rather than trusting one spot number.

Start with the room, not the mattress. Run the monitor in the empty bedroom for a full day first. Sensirion specifies a one-hour switch-on time (VisiblAir), and when sensors are placed in a common room with different histories, all VOC Index signals usually converge within 1 to 12 h (Sensirion). A reading taken minutes after you plug the monitor in tells you little.

Unwrap the mattress with a window open and the door propped. Place the monitor near pillow height, because the crib study found the breathing zone well above room air. Note the reading every few hours on day one, then each morning and evening for a week.

Watch which way the number moves. You should see a jump at unwrapping and then a fall over several days. If your device shows an index, its algorithm starts going back to average VOC Index after 3 h for very long events, so a return to 100 does not prove the emissions stopped.

One researcher went further. A co-author suggested parents could set aside a new mattress for six months, allowing it to give off most of its VOCs before bringing it in the house (C&EN, 2014). Airing a mattress before use cuts into the first-days peak, when emissions are highest. EWG adds that airing out a new mattress can reduce VOCs, but other harmful chemicals could still be present (EWG).

Which VOC readings should make you do something?

Our judgment on common reading patterns: direction and persistence tell you more than the size of a number from an uncalibrated home sensor.

The table below is our own judgment, built from the studies above. No maker publishes it, and it is meant for readings from a home monitor, not a lab report.

The EPA lists paints, cleaners, cosmetics and fuels among common household sources. It also notes that during and for several hours immediately after activities such as paint stripping, levels may be 1,000 times background outdoor levels (EPA). Before you blame the mattress, rule out the bottle under the sink. If a reading stays high past the first month, a lab test for formaldehyde and individual VOCs will tell you more than a second consumer monitor would.

Common questions

Short answers to the questions people tend to ask after they unwrap a new mattress and see a VOC number climb on a home monitor.

How long does a new mattress off-gas?

In the 2022 memory foam study, emissions peaked on the first day and fell over the next 31 days. Short-term emission half-lives for individual chemicals were on the order of hours (approximately 4 or 12 h) (Beckett et al., 2022). Emissions do not stop at one month, but the modeled one-year averages were small. Air the room hardest in the first week.

Is a VOC reading of 500 ppb bad?

From a low-cost monitor, you cannot say. AirGradient states that any absolute TVOC concentration output (e.g., "500 ppb" or "0.5 mg/m³") is not scientifically reliable from a low-cost MOx sensor (AirGradient). Compare the number with your own room's baseline and watch whether it is rising or falling.

Does airing out a new mattress help?

Yes, most of all in the first hours and days, when the short half-lives in the memory foam study mean emissions fall fastest. Airing does not remove the heavier chemicals that a TVOC figure leaves out, as EWG notes (EWG). An open window in the first week gives the biggest return.

Should parents worry more about a crib mattress?

Babies sleep for much of the day, and the Texas researcher noted that infants spend 50 to 60 percent of their day sleeping (UT Austin). In Toronto, researchers measured 25 bedrooms of children aged 6 months to 4 years and found the highest levels lurking around the beds (EurekAlert).

Which label limits emissions from the whole mattress?

GREENGUARD Gold has criteria for finished furniture and mattresses, while CertiPUR-US covers only the foam inside. If you see a CertiPUR-US claim, check the program's directory. If a company promoting its participation is not listed on the site, the program says it can't vouch for their use of certified foam (CertiPUR-US FAQ).

Does opening a window lower the reading?

It should. The German scheme calls for increased ventilation once total VOCs pass 300 µg/m³ (PubMed), and the EPA advises people to increase ventilation when using products that emit VOCs (EPA). A drop after you open the window also shows your monitor is responding.