Denver city officials are moving to ban the amateur use of a risky hash oil extraction process that has resulted this year in dozens of home explosions statewide.

A new proposal backed by Mayor Michael Hancock’s administration would ban the home use of solvent-based hash oil extraction. It involves highly flammable compressed gasses, typically butane, in the extraction of oil from marijuana. An additional risk is that some users stock up on those gases in their homes.

Licensed grow houses and other business still would be able to use the gas-based process, given that they take myriad precautions required by state law.

But Denver’s restrictions — among the first in the state — would limit those seeking to extract hash oil without a license to using safer water- and food-based methods. Or they could just buy hash oil at a dispensary.

“Clearly, the hash-oil extraction process creates a danger in our neighborhoods,” Hancock said. “We want to address it quickly.”

The council’s Safety and Well-Being Committee will consider the proposal Sept. 16.

Denver’s proposed ordinance comes as the City Council is set Sept. 15 to consider a zoning amendment that would close a loophole allowing residents in some parts of the city to grow more marijuana plants for personal use than in others.

The loophole resulted from an oversight when the council passed plant restrictions last year. It capped homegrows at six plants per adult and 12 per household and required them to be indoors. But the council inserted those limits into the city’s new zoning code, mistakenly leaving out grandfathered zoning areas that include Stapleton and Lowry.

Together, the two measures underline the trial-and-error reality facing local and state regulators of legalized recreational marijuana in Colorado.

“This is an evolving, dynamic process where we’re all going to be educated,” Hancock said.

Denver’s proposed hash oil restriction would follow recent restrictions or total extraction bans adopted by Centennial, Greenwood Village, Cortez and Telluride, according to the Colorado Municipal League. San Miguel County also adopted a ban on extraction using gas.

Those measure are coming in response to a spate of explosions that, in some cases, have resulted in serious injuries or even death. Earlier this week, Aurora and South Metro firefighters demonstrated the risks by blowing up a shed.

In Denver, which reported one blast last year from hash oil extraction, eight explosions have occurred so far in 2014. Statewide, officials report more than 30 such explosions this year.

Denver Fire Chief Eric Tade said in a statement that the gas-based extraction method “has proliferated in recent months and public safety concerns require action now.”

Home-based extractors seek to produce hash oil that has a consistency similar to jelly and can contain more than 75 percent THC, marijuana’s psychoactive chemical.

It’s much more potent than a joint.

Using the gas method, extractors typically stuff marijuana into a slender pipe and then blow compressed butane gas through it. This releases flammable butane fumes into the room that can ignite at any spark.

While those responsible for explosions can face criminal charges, the aim of the new local laws is to prevent them.

Licensed grow houses and other businesses that use the extraction method are required by state regulations to use ventilation hoods and a “professional grade, closed-loop extraction system.”

“It’s a huge responsibility to do this safely. And we also inspect them annually for that,” said Ashley Kilroy, Hancock’s executive director for marijuana policy.

Amateur extractors who violate Denver’s proposed ordinance would face up to a year in jail and a fine of up to $999.

Some backers of Amendment 64, which Colorado voters passed in 2012, have been skeptical about the extent of hash-oil extraction risks, but one co-author said local restrictions are appropriate.

“There is a public safety issue here, though I’m not convinced it’s of an outrageous proportion,” attorney Brian Vicente said. “If communities need to have restrictive laws on the books to make them feel safer, they should do so.”

Jon Murray: 303-954-1405, jmurray@denverpost.com or twitter.com/JonMurray