FORNEY — Shortly after graduating from college, Walton McCarthy went to a party where he overheard a disturbing conversation between a child and her mother.

"The little girl said, "Mommy, if I grow up, can I be an architect and design things?" McCarthy recalled.

McCarthy wondered why the child had said if she grows up and assumed she was terminally ill. The mother later told him that they had a "euthanasia plan."

"If there was a nuclear exchange, they would euthanize themselves," McCarthy said. "It’s not something that people talk about now, but in 1978 . . . It really, really scared me. I started doing some homework and one thing led to another."

McCarthy, who has a mechanical engineering degree, started designing bomb shelters. First, they were made out of concrete and steel. But for the past two decades, McCarthy — the author of Principles of Protection: The U.S. handbook of NBC Weapon Fundamentals and Shelter Engineering Design Standards — has been manufacturing underground fiberglass disaster shelters.

Recently, the Star-Telegram sat down with McCarthy, 57, to learn about his company, Radius Engineering International, which is based in Forney, a small town east of Dallas.

Tell me about your business.

We manufacture underground disaster shelters for nuclear, chemical and biological warfare. They will also work for tornadoes, hurricanes . . . they are set up to protect people anywhere from 30 days to five years.

What are the different models, and how much do they cost?

The most common model is called a P-10. It is a 10-person shelter and it is $105,000. The Cat 25 is $340,000 and it has facilities for 25 people. There are two bathrooms, two showers, a media system, cooking facilities, alcohol stoves. The third is called the Ethos community. For 300 people, it is about $6 million. We have a number of them out there.

Who buys your shelters?

Key executives, physicians, technical people and government personnel. Political people in Washington, D.C., are about half of our market.

How has business been lately?

We have 48 people [employees] and we need to get to 148 by the end of the year to keep up with the demand. We are swamped.

If a nuclear bomb hits, how long will people have to stay in a disaster shelter?

Not longer than 30 days. Thirty days after a nuclear weapon detonates the radiation levels are basically back to normal. Any food that is in a plastic bag or a can would be safe to eat. You can decontaminate water pretty easily, but water doesn’t become radioactive.

A lot of people can’t afford a shelter. How can they protect themselves?

The first thing is education — understand what the real effects of the weapons are. Gas masks will get you somewhere but you can’t wear them for more than a couple of hours. You can make one room in your house safe.

Do you have a disaster shelter for you and your family?

I share one with another family, a physician just outside of Dallas. It is a Cat-25. I also have a thousand across the country [that Radius manufactured and installed]. I have better protection than the president because I have one in every major city.