The playground padlocks are starting to come off. Now that all 50 states have begun to reopen, children in some areas are once again zipping down slides and swinging from monkey bars after months of waiting.

A handful of states, including Massachusetts, Colorado, Ohio and Iowa, announced in June that playgrounds could start reopening, though the decision to open town or city-owned playgrounds is usually made locally. In Boston, for example, playgrounds are not expected to open until next week. On Thursday, Gov. Andrew M. Cuomo of New York said during his daily briefing that localities are now permitted to open public pools and playgrounds, and local governments can decide for themselves whether or not to do so.

“But they have to use their judgment here,” he said. “Sometimes ‘yes’ is not the right answer. It’s the easy answer.”

While this is good news for children, some parents are being a bit more cautious. The coronavirus is still spreading, and a vaccine isn’t expected until next year at the earliest. Although the overall number of deaths in the United States has been curving downward, testing in some states suggests that infections are climbing quickly. So is it really OK to return to the playground?

Are playgrounds safe now?

It’s impossible to negate all risks of contracting the virus at a place like a playground, which is frequented by large numbers of people who may have different views about social distancing and hygiene.

But outdoor playgrounds do have the benefit of fresh air and more space between people than what most indoor spaces offer. There is a growing consensus that if you’re going to leave your home, it’s safer to be outdoors than in an indoor public gathering space, like a mall. When air is stagnant, respiratory droplets could linger, experts say, whereas the air flow outside can help dilute the virus.

A crowded playground, however, might present a bigger risk.

In Massachusetts, caregivers “will be required to seek alternative facilities” if the playground is so crowded that social distancing cannot be maintained, according to the Executive Office of Energy and Environmental Affairs.

Colorado has more specific rules about capacity. Playgrounds can be used by no more than 25 people at a time, the Colorado Department of Public Health and Environment announced last week, and high touch areas should be cleaned and disinfected “frequently.”

Can the virus live on playground surfaces?

It’s unclear how long the coronavirus can live on plastic and metal playground structures that are touched by hundreds of tiny, and often dirty, hands.

The Centers for Disease Control and Prevention has said that people can get Covid-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose or eyes, but this was “not thought to be the main way the virus spreads.”

A study published in The New England Journal of Medicine found that the virus lives longest on plastic and stainless steel and can survive on those surfaces for up to 72 hours. Another study, published in The Lancet, found that the Covid-19 virus remained viable up to four days on stainless steel and plastic, but the researchers said the method they used to extract the virus from these objects wasn’t analogous to casually touching a surface.

The World Health Organization cautioned that those studies were conducted under laboratory conditions where the surfaces were neither cleaned nor disinfected so they “should be interpreted with caution in the real-world environment.” And it’s also unclear whether the virus the researchers detected would have infected people who came in contact with these surfaces.

The C.D.C. recommends that playground surfaces made of plastic or metal, like grab bars and railings, be cleaned regularly, but said they do not require disinfection.

And not all administrators have the funds to clean playgrounds. In Iowa, the Department of Natural Resources posted on its website, “Equipment is not sanitized, user discretion is advised.”

Some studies suggest that sunlight could help to reduce the amount of virus lingering on surfaces, but that doesn’t appear to have been studied in playgrounds.

Should children wear a mask at the playground?

Yes, the C.D.C. recommends wearing masks in playgrounds. Face coverings are believed to reduce transmission of the virus. Even the World Health Organization, which had long refused to endorse face masks, concluded in June that governments should encourage mask wearing because of “a growing compendium of observational evidence.”

Cloth masks worn by the general public aren’t as effective as surgical masks or N95 respirators, but they still offer some barrier protection against the large respiratory droplets generated when an infected person sneezes, coughs or breathes.

But for very young children, say 2 or 3 years old, wearing a mask can sometimes be counterproductive, said Dr. Sean O’Leary, M.D., the vice chair of the American Academy of Pediatrics’ Committee on Infectious Diseases and an associate professor of pediatrics at the University of Colorado Anschutz Medical Campus and Children’s Hospital Colorado.

For example, if your child is continually touching their face and readjusting the mask, “they might become infected themselves,” Dr. O’Leary said.

The C.D.C. says children younger than 2 should not wear face coverings because of the risk of suffocation.

What else can caregivers do to protect themselves and children at playgrounds?

If a playground is full of children, consider coming back at a different time of day — perhaps early in the morning when the crowds are thinner.

If there aren’t bathrooms nearby to wash children’s hands regularly, the C.D.C. recommends carrying hand sanitizer. Apply enough to coat every surface of both hands and then tell your child to rub their hands together until they are dry. Consider cleaning your child’s hands before they eat a snack on the playground and also after leaving it.

If you plan to use sanitizer, it’s wise to have a bottle of water on hand as well. That way, if your child’s hands become covered in dirt or sand you can rinse them off before applying the sanitizer. The C.D.C. says that sanitizer is less effective on dirty or greasy hands.

Finally, don’t assume that the children are the primary vectors of disease. Adults spread the virus more readily than children, Dr. O’Leary said.

“That’s why the adults that are supervising should be careful about staying away from other folks,” Dr. O’Leary said.

Why isn’t my playground open yet?

Some localities, especially dense urban cities like Chicago, Los Angeles and New York, have decided that playgrounds present too much of a risk right now.

“The day is coming, it’s not here yet, but the day is coming we’ll be able to open up them again,” Mayor Bill de Blasio said during a news conference on Thursday. “We don’t have a timeline yet.”

Jane Meyer, a spokeswoman for the mayor, said in an interview this week that there are no immediate plans to reopen playgrounds in New York City, in part because playground equipment makes it tough for children to physically distance from each other.

“Depending on the age of the kid, it’s extremely difficult if not impossible to control exactly how close they are,” she said. “Everything we do is weighing the risk against the reward.”

To give children more space to play, New York City has opted to close certain streets to vehicle traffic and will also be setting up water misters in some parks.

The National Recreation and Park Association has recommended that playgrounds stay closed until there is no longer widespread community transmission of the virus because playgrounds have a tendency to become crowded and it is difficult to keep surfaces clean and disinfected.

The C.D.C. has also said that playgrounds are difficult to keep safe.

“Now in reopening, we have to actually double-down on our diligence,” Mr. Cuomo said on Wednesday. If people continue to use hand sanitizer, stay away from large gatherings, wear masks, and stay physically distanced, he continued, “the virus spread will be contained.”