Sometimes it’s best to let the kids play indoors. It sounds like heresy coming from a hippie-mother type like me. We’re conditioned to want our kids to play outside, get fresh air, get dirty, get off the couch and stay away from the tube.

But, there’s another issue to consider — isn’t there always? — for families in urban and suburban areas. That gross, stagnant, muggy air may not be something you want your kids breathing during peak smog hours.

The Environmental Protection Agency warns of serious health problems such as chronic bronchitis and aggravated asthma associated with ozone and fine particle pollution caused by auto emissions and other pollutants. Small particles, which are found in haze, can cause the most damage, getting deep into your lungs and into the bloodstream, according to the EPA.

Children and older adults are the most vulnerable, but even healthy adults can be at risk when particle pollution or ozone is high.

I have heard this message for years. Living in Atlanta during the summer, I can get smog alerts delivered right to my e-mail inbox.

And, yet, I encourage my daughter to play outside as much as possible, even on hot, muggy days. Even when she was an infant, I strolled her for miles through our neighborhood despite smog.

I buy organic food. I used cloth diapers and glass baby bottles. I scan lists of toys recalled for lead paint. Yet I inexplicably fail to adopt this obvious, low-effort green-mom protocol of keeping my daughter indoors when the air pollution is high. Yes, she’s healthy. She has never shown signs of asthma. Still, it’s clear from EPA reports that I should be protecting us both.

For insight as to why I don’t make this issue a priority, I called my friend Rebecca Watts Hull, program manager for Mothers & Others for Clean Air at the Georgia Conservancy. Founded by two of Atlanta’s most vocal green moms, Laura Turner Seydel and Stephanie Blank, the program works to improve air quality and educate Georgians about why clean air is important.

Rebecca says air quality can be a hard issue to generate interest in, even among otherwise eco-sensitive parents. “It’s hard to make the air issue tangible,” she says, adding that the organization’s campaign for more environmentally safe school buses has been an easier sell. “You can see school bus soot. You can smell the fumes.”

In Atlanta, we’ve enjoyed a mild summer this year. I don’t want to jinx it, but it would not be an exaggeration to describe some of our days as cool and comfortable. For Rebecca, that just makes education harder. “We know we need to continue to reduce emissions,” she says. “This year we’ve just been lucky.”

The message for parents is simple. This map will tell you whether your area is at risk for dangerous fine particle pollution. The government’s AirNow site rates current air quality as good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy or hazardous.

If you live in an area with a serious pollution problem, your local government may issue alerts the day before a bad air day. The AirNow site will connect you to local resources.

Ozone levels peak between 2 and 7 p.m., which means it’s generally safe for your child to play outside before 2 p.m. on ozone-alert days. For small particle pollution, known as PM, the air is worst around morning and evening rush hours, but can remain bad all day. It’s best to mostly play indoors on such days, Rebecca says. And if it’s a bad day for ozone and PM, it’s safest to avoid playing outside altogether. “Great day for a movie!”

Parents should work with their child’s daycare or school to make sure kids aren’t on the playground during unsafe times. (This, too, can be tough, Rebecca says, noting that schools with the most progressive reputations can be fervid in their commitment to having kids play outdoors.) After-school program directors and coaches may also need persuading.

Rebecca’s kids haven’t been hard to convince. “The kids get it,” she says. “They understand this isn’t an arbitrary rule Mom made up to be mean.”

She points out that there are plenty of games and activities kids can do indoors to burn calories and blow off steam.

I’m going to try harder to heed the warnings and play indoors with Celia when the air is heavy with pollution. The truth is, I like lounging on the couch and watching the tube now and then. Celia will, too.