How long volatile organic compounds (VOCs) last after painting primarily depends on which type of paint you used. Oil-based solvent-based paints are drastically different from the best zero-VOC water-based paint.
It also depends on your humidity, temperature, and ventilation.
We lack independent studies looking at the offgassing of each main paint type but we do have exact data from specific paint companies.
If you have already painted and are trying to determine if it’s still offgassing you must find out what kind of paint it is and then see if you can find the brand and sub-line. If you don’t have the brand name you can compare it to a major brand to get an idea.
Remember that paint has improved significantly in the last few years, almost all brands have zero-VOC and ultra-low VOC lines. This is no longer a specialty product. So past reports on how long it took paint to offgas are no longer accurate as they were based on higher VOC products.
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Which VOCs Offgas from Paint
Commercially available water-based emulsion paints were tested using the European standard test method. In total, 23 individual volatile organic compounds (VOCs) were detected and quantified. The seven major VOCs were 1-ethyl-3-methylbenzene, followed by 1,2,4-trimethylbenzene, n-hexane, 1,3,5-trimethylbenzene, propylbenzene, o-xylene and toluene (source).
Keep in mind that there are 37 exempt VOCs – VOCs that could be in paint but are not counted in their VOC rating. These include ammonia, acetone, and butyl acetate, which are commonly used in consumer paints, says Andy Pace.
Type of Paint Affects Offgassing of VOCS
Remember that there is a huge difference in VOCs between different types of paints.
- Oil-based paints – which are not used as often now, still are sometimes used on trim and doors, and occasionally as a primer. This is the highest offgassing paint and the slowest to offgas. VOCs start in the hundreds of grams per liter.
- Spray paints – spray paints are also usually solvent-based. Spray paints come in between 400-600 g/l VOCs.
- Water-based alkyd paints – these are the newer replacements for oil-based paints that are often used on doors and trim. They are much lower VOC than oil-based paints and can be relatively fast to offgas. They are higher VOC than many wall paints. VOCs are around or under 50 g/l.
- Low-VOC wall paint – while I would always aim for 0-VOC wall paints, low-VOC wall paints are still used and come in as high as 50 g/l VOC.
- Zero-VOC wall paint – this is my preferred type of wall paint. You will need to ask the company at how many hours or days is it 0-VOC (and I have some of that data below).
- Primers – while some companies like ECOS Paints makes 0-VOC primers, typically, water-based primers are higher in VOCs than paint and might come in around 50 g/l or less.
When is the Majority of the Offgassing Complete
In one study that looks at interior water-based and oil-based paints they found that extended emission tests showed that most VOC and intermediate VOC emissions occur within 12–24 hours after the paint application, though some paints continue to emit intermediate VOCs for 48 hours or more (source).
Individual Paint Brands and Offgassing Times
You can get specifics of general information on how long a paint takes to offgas by asking the manufacturer. They may provide the official day that the paint has tested 0-VOC or they may provide you with the cure time (which is not exactly the same as the time it needs to offgas but it gives you some framework. Paint companies tend to conflate cure times with offgassing time which can make their estimates overly generous), or the time that they say it’s safe to re-enter the room (which is also not necessarily when it has reached 0-VOC status).
ECOS Paints – officially the VOC testing was done at 11 days (per the CDPH 01350 test methodology), and that is when the zero-VOC measurement was taken.
Kiem Mineral Wall Paint – because this paint uses mostly benign mineral binders it offgasses very fast (faster than an acrylic 0-VOC paint). There is no offgassing after the paint has dried – in approximately 2 hours at 77 degrees and 50% relative humidity, explains Roy Suttles a rep for the company.
Benjamin Moore – “After seven days, off-gassing is reduced to a minimal or acceptable level according to the California Department of Public Health, which both Eco Spec and Ben (0-VOC lines) are tested against” says rep David Underwood, Associate Technical Project Manager at Benjamin Moore.
As for Ben Moore Advance (a water-based alkyd), a rep for Benjamin Moore said on the phone that Advance takes 2-3 weeks for a full cure and to finish offgassing. It also says on the website that depending on the temperature and humidity, it could take up to 30 days to reach optimum hardness and final sheen.
Sherwin-Williams ProClassic Interior Water-Based Acrylic-Alkyd – this is another water-based alkyd paint. This comes in at 14 g/l VOC. Give it 2-4 weeks for a full cure, which is when it’s offgassed, they say on the phone.
Farrow and Ball – Farrow and Ball Estate Emulsion is a non-acrylic paint, which uses a VAE (vinyl acetate ethylene) binder instead. The VOCs when wet are only 4 g/l and at 28 days the emissions are 47 µg/m3.
Rust-Oleum – Rust-Oleum has said that that Universal line which includes Spray Matte, Metallic, and Stops Rust Protective Enamel (which is the same as the Premium Metal Protection I tested in Silver) all take 7-10 days to cure. However, offgassing can continue at detectable levels for 4-5 weeks or more for these solvent-based spray paints.
Recommendations on Ventilation
The Department of Environmental Protection, Montgomery County Maryland, recommends ventilation after applying latex paint at least 48 hours and preferably for 72 hours (source).
Humidity and temperature also affect offgassing times. Be sure you are within the range that the company specifies. And after painting, to speed up offgassing, ideally keep humidity low and temperature up while maintaining ventilation.
Experiences of the Chemically Sensitive
Even though paint offgasses the majority, or even vast majority, of its VOCs in the first three days, and even after a paint has officially hit its cure time, there can still be offgassing of unreacted monomers which the chemically sensitive can react to (source).
The most extremely chemically sensitive folks who I have worked with over the last 10 years have sometimes needed to give ECOS Paint 2 weeks to offgas, other zero-VOC brands up to 4 weeks (and sometimes months), low-VOC water-based paint many months (or even longer for older formulas), and oil-based (solvent-based) paint can cause reactions for years.
Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.