Does Rubber Mulch Smell? How Long It Lasts and What Helps

Yes, new rubber mulch has a rubber smell, but not for very long.

It is usually strongest right after it is delivered and spread, and it fades with time. Some people compare it to a new shower curtain or a tire shop. It is stronger on hot days for some people. How long it lasts varies, and no published test gives a number.

What does rubber mulch smell like?

Like rubber. The Alabama Department of Environmental Management's scrap tire program says the smell may be noticeable at first and fades with time, similar to that of a new shower curtain. Others are less gentle: a Southern Living columnist says on a hot summer day it smells like hot tires. Both are describing the same rubber odor. How strong it seems depends on how much you have, where you spread it and how sensitive you are to it.

How long does the smell last?

There is no published measurement of how long the odor lasts for loose rubber mulch, so we will not give a number. State guidance says it fades with time. Customer reviews of other brands on Home Depot describe it going away after a couple of weeks. Plan on days to a few weeks, and expect a larger area to smell more than a small bed.

Does rubber mulch smell more when it is hot?

It can. Customers and reviewers often say so, and there is some lab support. In EPA's testing of tire crumb rubber (the infill used on synthetic turf fields, which is a different use from mulch), air emissions were low at 77 degrees F, and higher at 140 degrees F for some, but not all, of the chemicals measured. EPA chose those temperatures to represent moderate and high-end field conditions. We do not have a measurement for mulch itself. Dark rubber also gets hotter in the sun, so shade and lighter colors may help. See does rubber mulch get hot.

Is the smell harmful?

A smell by itself does not tell you whether a product is safe. What the agencies say:

• CPSC: it knows of no specific chemical hazards from recycled tires in playground surfacing at this time, says it is evaluating the latest federal research, and recommends avoiding mouth contact with the material, washing hands after play and limiting time on playgrounds on extremely hot days.

• EPA and CDC/ATSDR: their research on tire crumb rubber on synthetic turf fields concluded that chemicals are present, exposures can occur, and exposures are likely limited, with only small amounts of most organic chemicals released into the air. That research is about turf fields, not mulch beds.

If you want to know what is in a specific product, ask the seller for its test reports. For playground use, the CPSC's handbook says rubber mulch should meet ASTM F3012. The Playsafer spec sheet lists F3012 hazardous metals, lead, tramp metal and sieve results as Pass.

What can help while it airs out?

These are practical suggestions rather than tested results:

• Spread it outdoors in the open air rather than keeping open bags in a closed garage or shed.

• Give it time before judging. The odor is strongest at the start.

• Use shade or lighter colors where heat will be an issue. They stay cooler, and heat tends to bring out the smell.

• Think about placement. If you or a neighbor are sensitive to odors, start with a smaller area or keep fresh material away from open windows and air intakes for the first weeks.

Does wood mulch smell too?

Fresh wood mulch smells like cut wood or soil. It can also go "sour." The University of Massachusetts says sour mulch smells like vinegar, ammonia, sulfur or silage, and Iowa State Extension explains it happens when mulch is stored in excessively large piles or saturated conditions, creating low-oxygen conditions in which microbes ferment it. Because rubber mulch is not decomposing plant material, sour mulch does not apply to it. A vinegar or ammonia smell points to organic mulch that has gone sour, not to rubber. See our rubber mulch vs. wood mulch comparison.

FAQ 

Q: Does rubber mulch smell?
A: Yes. New rubber mulch has a rubber odor, strongest right after delivery, that fades with time. The Alabama Department of Environmental Management compares it to a new shower curtain.

Q: How long does the rubber mulch smell last?
A: There is no published measurement. Expect days to a few weeks, depending on how much you spread, the weather and your sensitivity. State guidance says it fades with time, and customer reviews of other brands describe a week or two.

Q: Does rubber mulch smell more when it is hot?
A: It can. Many people say so, and EPA lab tests of tire crumb rubber found higher emissions of some chemicals at 140 degrees F than at 77. That research is about turf infill, not mulch. Shade and lighter colors keep rubber cooler.

Q: Does rubber mulch smell like tires?
A: Many people describe it that way, especially in warm weather. It is rubber, and the odor is similar.

Q: Is the smell of rubber mulch dangerous?
A: Smell alone does not show whether a product is safe. The CPSC says it knows of no specific chemical hazards from recycled tires in playground surfacing at this time and is continuing its review. Ask the seller for test reports, and for a playground, check that the mulch meets ASTM F3012.

Q: How can I reduce the smell of rubber mulch?
A: Spread it outdoors in open air, give it time, use shade or lighter colors where heat is a concern, and keep fresh mulch away from open windows and air intakes at first. These are practical suggestions rather than tested results.

Q: Why does wood mulch smell like vinegar or ammonia?
A: That is "sour mulch," a problem of organic mulch that was piled too high or kept too wet and ran low on oxygen. Rubber mulch is not decomposing plant material, so it does not go sour.

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