If a positive angle can be found in the tragic explosion of the London School on March 18, 1937, it could be that hundreds, if not thousands, of lives have probably been saved as a result, according to Archie McDonald.

"The major positive that came from the New London school explosion was legislation requiring gas companies to add an odor to their product so anyone can determine when natural gas is leaking or not properly utilized," said McDonald, a historian long associated with Stephen F. Austin State University who has researched the topic.

Click the image above for an audio slideshow in the survivors own words. Click the image above to see a video on London history. Click the image above for more photos. MORE NEW LONDON STORIES: Cenotaph honors those killed in school explosion  London Museum houses items from tragic day  Cemetery home to 129 killed in blast  Through their eyes: Four survivors discuss how the New London explosion changed them forever  During oil boom, before explosion, the school was the PRIDE of New London  Reporters converge on New London  Odor now added to natural gas  Community gathers to honor those who died in school explosion and those who lived  Faces, forever changed: School blast survivors still unable to talk about those they lost  Remembrances roll as London School graduates gather  Silence was normal for many survivors  A shared pain: London School graduates gather to mark blast's 70th anniversary  Explosion survivor's faith still strong after tragedy

Naturally, natural gas has no odor. The smell today many associate with the release of natural gas comes from a malodorant agent added to the gas just for the purpose of allowing it to be smelled should a leak develop.

What some people describe as a rotting cabbage smell usually associated with natural gas comes not from natural gas itself but from mercaptans, which are added to natural gas during processing.

The London School can be credited with instigating, or at least speeding up and stimulating, laws resulting in requiring the odor agent to be added, McDonald said.

The April 1937 edition of the Quarterly of the National Fire Protection Association ran a 14-page summary of the London School disaster of the previous month. Among the conclusions in the report prepared by H. Oram Smith with the Texas Inspection Bureau, was that "the value of a distinctive malodorant in all gas supply systems by which leaking gas may be readily detected is clearly evident."

Smith wrote there was only one explosion associated with the disaster and no fire.

"Yet there is evidence of a most terrific force in the great extent of devastation and loss of life that came almost instantly; testimony of bodies tossed 75 feet in the air; an automobile 200 feet distant crushed like an eggshell under a two-ton slab of concrete that had been hurled from the building," Smith wrote. He said at the established point of origin of the blast the explosion had to "break through an 8-inch concrete floor slab before starting on its path of destruction."

In the Texas Railroad Commission archives covering a summary of the agency's activities in the 1930s was an item indicating enforcement of the new rules requiring odorants was enacted, said Ramona Nye, spokeswoman for the agency.

"As a result of this tragedy, the 45th Legislature enacted House Bill 1017 ... giving the Railroad Commission the authority to adopt rules and regulations pertaining to the odorization of natural gas or liquefied petroleum gases," the commission archives said. "On July 27, 1937, Gas Utilities Docket 122 was adopted and the commission began enforcement of odorization requirements for natural gas."

In May 1937, the Texas Railroad Commission, at the time referred to as the most powerful board of resource regulators in the world, had passed an order in memory of those killed in New London that continues to impact the lives of people worldwide.

Shortly after the disaster, the Texas Legislature met in emergency session and enacted the Engineering Registration Act, now rewritten as the Texas Engineering Practice Act. Public pressure was on the government to regulate the practice of engineering because of the faulty installation of the natural gas connection at the London School believed to have resulted in the natural gas leak.

Many other states soon enacted rules requiring an odorant be added to natural gas, and later in 1937 federal requirements were made law, Smith said.

According to the Texas Railroad Commission, the odorants are considered non-toxic in the extremely low concentrations occurring in natural gas delivered to the end user.