Playground Safety Guide

Understanding Impact Attenuation: G-max & HIC

Two numbers decide whether a playground surface passes, and labs call them G-max and HIC. Both come from ASTM International test methods, and both are read the same way. A lab drops a weighted headform onto the surface and records what happens. Once you know what each number means, you can judge any surfacing claim you read, and you can ask a supplier the right question.

“Use Zone — The surface under and around a piece of equipment onto which a child falling from or exiting from the equipment would be expected to land.”

U.S. Consumer Product Safety Commission, Public Playground Safety Handbook (Publication 325)

“Critical Height — The fall height below which a life-threatening head injury would not be expected to occur.”

U.S. Consumer Product Safety Commission, Public Playground Safety Handbook (Publication 325)

“There are also rubber mulch products that are designed specifically for use as playground surfacing. Make sure they have been tested to and comply with ASTM F1292.”

U.S. Consumer Product Safety Commission, Public Playground Safety Handbook (Publication 325), section 2.4.2.2.

What Is G-max?

G-max is the peak force of an impact, or simply how hard the stop is. A lab drops a headform onto the surface from a set height, and sensors inside record how fast it slows down. That reading is the G-max. A low number means a soft landing, and a high number means a hard one.

Threshold: ASTM F1292 sets the top limit at 200g, and a surface that reads above that limit does not pass.

ASTM F1292, the impact-attenuation standard for playground surfacing.

What Is HIC (Head Injury Criterion)?

HIC stands for Head Injury Criterion, and it weighs force and time together rather than force alone. A short, sharp stop and a longer, gentler one can read the same on G-max, but HIC tells those two apart. That is why a lab runs it next to G-max, and why the pair gives a fuller picture of a fall.

Threshold: ASTM F1292 sets the top limit at 1,000, drawn from research that links HIC scores to head injury.

Tested to ASTM F1292. The head-injury measure it uses dates to Versace (1971).

Why Both Metrics Matter

A surface can pass one test and miss the other, so both have to sit inside the limits to count as compliant. Depth is the thing that moves both numbers. A thin layer reads high, and a deeper layer reads lower. Softscape Outdoor mulch is lab tested against both of those limits.

Critical Fall Height (CFH) Reference Table

Critical Fall Height is the tallest fall a surface can handle. Above that height, the surface no longer holds G-max and HIC inside their limits. The task is simple enough: find the highest point a child can reach on your equipment, then install the mulch depth that matches it. The table below pairs the two for you.

U.S. Consumer Product Safety Commission, Public Playground Safety Handbook (Publication 325), Table 2.

Read the third column against your equipment. Find the highest point a child can reach, then read across to a material and depth that protects to at least that height. The depth in the first column is what has to stay on the ground, not only what you spread on the first day. The handbook’s own note is to keep that depth constant, because displacement can still happen.

“Never use less than 9 inches of loose-fill material except for shredded/recycled rubber (6 inches recommended).”

U.S. Consumer Product Safety Commission, Public Playground Safety Handbook (Publication 325), section 2.4.2.2.

Important: These figures are Table 2 of the CPSC Public Playground Safety Handbook, and they are the handbook’s minimum depths. Your equipment maker may call for more depth, and your local rules may call for more as well. Check both before you set a final depth.

Governing Safety Standards

A handful of documents govern playground surfacing in the United States. Two of them are test methods, one covers access, one is a third-party check, and one is the federal handbook. Here is what each of them covers, in plain terms.

ASTM F1292 · IPEMA certification database · CPSC Public Playground Safety Handbook.

Is Rubber Mulch Flammable?

Rubber mulch can burn. It is not sold as a fire-safe material, and no rubber surfacing product is. Treat it the way you would treat any loose ground cover near a heat source, and keep fireworks and smoking away from the play area.

Practical safety measures:

• Keep smoking and open flames away from the play area, which is standard practice for any surface.
• Store fuel and chemicals well away from mulched areas.
• Follow the local fire code that covers your facility.

Does Rubber Mulch Get Hot?

Yes, it warms up in direct sun, and so does every other playground surface. Asphalt, sand, and synthetic turf all heat up on a sunny afternoon. Sun and shade drive this far more than the material itself does. The good news is that shade works, and it works quickly.

Heat Management Strategies

• Shade: Trees, canopies, and shade sails all bring the surface temperature down, and this is the biggest lever you have.
• Timing: Midday is the hottest stretch of the day, so morning and evening play is cooler.
• Layout: Set equipment where nearby trees or buildings cast shade during play hours.
• Check by hand: Touch the surface before play on a hot day, the same way you would check a metal slide.

Is It Safe for Kids?

Yes. Installed at the right depth for your equipment height, rubber mulch gives tested fall protection, and the material itself is inert. Public playgrounds across the country have used it for many years, and it is a familiar choice for schools and parks.

Depth is the part that carries the protection, so getting it right on day one is only half the job. Check the depth again through the season, above all under swings and at the foot of slides. Those are the spots where children land hardest and most often.

For more on toxicity and general health questions, see our dedicated pages: Is Rubber Mulch Safe? and our frequently asked questions.

Does It Attract Bugs or Pests?

No. Insects come for food and damp shelter, and rubber gives them neither. Wood mulch is a different story, because wood is organic. As it breaks down it can host termites, ants, and insects that feed on fungus. Wood also holds moisture longer, and damp ground is what many pests are after.

You may still find a spider or a ground beetle under a loose chip now and then. That is ordinary outdoor life, not a sign of an infestation.

Texas A&M AgriLife Extension, subterranean termites · Penn State Extension, Artillery Fungus in Mulch.

Does Rubber Mulch Float or Cause Drainage Issues?

Rubber mulch is heavier than water, so it does not float in normal use. Heavy flooding is a different case, because fast-moving water can push loose chips out of place. That is water moving the material, not the material floating on top of the water.

Drainage Performance

Water runs straight through loose rubber chips, so puddles are much less likely than on a hard, flat surface. In rainy regions that is a real gain. Slick, standing water is where falls happen, and a surface that drains well sheds the water instead of holding it.

Displacement Management

If your site floods, edging or a border helps hold the material in place. Check the depth after any heavy storm, and rake mulch back into the thin spots. Top it off when the depth drops under the minimum for your equipment height.

Ongoing Safety Maintenance

Safe surfacing is not a one-time job, because the depth you install is the depth you have to keep. A short routine covers it, and most of that routine takes only a few minutes.

• Check depth often: Hold the depth at or above the compacted minimum for your fall height, starting with the busy spots under swings and at slide exits.
• Inspect each quarter: Look for thin spots, packed areas, and debris that could change how the surface performs.
• Check after storms: Heavy rain, high wind, and snow all move loose material around.
• Get an annual review: Public sites should book a professional playground safety audit each year.
• Clear debris right away: Pick out glass and other sharp objects as soon as you spot them.

U.S. Consumer Product Safety Commission, Public Playground Safety Handbook (Publication 325), maintenance section.

Specify Softscape Outdoor for Your Playground Project

Every Softscape Outdoor product is IPEMA certified and tested to ASTM F1292, and every color meets that same standard. Pick the look you want, then match the depth to your equipment height.

You get a real delivered price, not a starting price. Order 1 to 7 pallets online, or ask us for a quote at any quantity. That covers everything from one backyard swing set to a full city park.

Delivery is curbside and the driver sets the pallets at the curb, where the order is in bags. A super sack comes off in one piece, so it needs a loading dock, or a forklift and a pallet jack.

View playground product specifications →