Federal regulators are beginning to crack down on a new generation of pipelines that will be crucial for the Biden administration’s plans to capture millions of tons of carbon dioxide to combat climate change.

The Pipeline and Hazardous Materials Safety Administration (PHMSA) proposed penalties yesterday on the operator of one such pipeline that ruptured in Mississippi, sending at least 45 people to the hospital in 2020. The agency also pledged to craft new rules to prevent similar pipeline failures from happening as the US makes plans to build out a network of pipelines to transport captured CO2.

There are not many of these pipelines (compared to oil and gas pipelines) yet in the US, which are primarily used by the fossil fuel industry so it can shoot CO2 into oil fields to push out hard-to-reach reserves. One of those pipelines ruptured in February 2020, releasing about 30,000 barrels of liquid carbon dioxide that immediately started to vaporize and triggered the evacuation of 200 residents in and around the small town of Satartia, Mississippi. Some of those who weren’t able to leave in time were left convulsing, confused, or unconscious, according to an investigation published last year by HuffPost and the Climate Investigations Center.

Pipelines for CO2 transport the gas at high pressure and at a high enough concentration to make it an asphyxiant. The CO2 in the pipeline that ruptured was also mixed with hydrogen sulfide, but CO2 can still be harmful on its own. About 100 workers a year die from CO2 accidents globally. It’s heavier than air, allowing a plume of it to sink to the ground and blanket a large area. That can also starve vehicles of oxygen it needs to burn fuel, which can strand people trying to evacuate or authorities trying to respond to the crisis.

PHMSA proposed $3,866,734 in penalties on the operator of the pipeline that busted open in 2020, Denbury Gulf Coast Pipeline, for “probable violations.” After investigating the incident, PHMSA says that Denbury did not report to authorities “at the earliest practicable moment” after detecting the CO2 release. That hindered first responders who were left to guess what was going on after receiving reports from residents of “a green gas” in the area.

PHMSA also says that Denbury failed to conduct routine inspections and lacked written procedures “for conducting normal operations, as well as those that would allow the operator to appropriately respond to emergencies, such as guidelines for communicating with emergency responders.” Specifically, PHMSA says Denbury couldn’t provide documentation to show that it had been in touch with local officials consistently on what to do in the event of an emergency involving its pipeline.

A statement emailed to The Verge by Denbury spokesperson Brad Whitmarsh says that the company plans to improve surveillance of its pipelines to prevent future problems and “work constructively with all federal, state, and local agencies.” The 2020 rupture occurred after heavy rains in the area caused the ground to shift, stressing the pipeline, according to Whitmarsh’s email.

PHMSA says it’s in the process of crafting new rules for CO2 pipelines, including requirements for how to respond to and prepare for emergencies. There is frighteningly little oversight of those pipelines, according to an assessment commissioned by the charity and advocacy group Pipeline Safety Trust that was published earlier this year.

In the meantime, PHMSA posted an advisory bulletin urging pipeline operators to plan ahead for risks posed by geohazards like those that caused the rupture near Satartia — especially as climate change leads to more extreme weather that can affect the stability of soil surrounding pipelines.

“As Denbury’s failure in Satartia, MS demonstrates, CO2 releases can be incredibly hazardous to our communities,” Pipeline Safety Trust Executive Director Bill Caram said in a press release. “The list of proposed new CO2 pipeline projects seems to grow every week, which makes it all the more important to modernize our safety regulations immediately.”

The Bipartisan Infrastructure Law that passed last year includes about $18 billion for projects that capture carbon dioxide from the air or from smokestack emissions. Those projects will rely on a new network of pipelines to move the greenhouse gas to places where it can be stored away, ostensibly preventing it from further heating up the planet. That means the US will have to figure out its pipeline problems if it wants to cope with climate change by capturing carbon dioxide.