Animal Protection Groups Call on USDA to Require Cameras Inside CO2 Stunning Areas of Pig Slaughter Plants

Pigs being positioned for loading into a CO2 gas system gondola at Smithfield Foods slaughter plant.
Still from video by Direct Action Everywhere

Washington, DC—Today, a coalition of animal protection groups submitted a rulemaking petition to the US Department of Agriculture to require pig slaughter plants to install cameras inside gondola cages used in carbon dioxide stunning systems. The petitioners are the Animal Welfare Institute, Compassion in World Farming, the Humane Society of the United States, Humane Society Legislative Fund, Humane Society Veterinary Medical Association, and World Animal Protection.

An estimated 90% of the 130 million pigs killed in the United States each year are slaughtered using CO2 gas, and recent undercover investigations in the United States and Australia have documented extensive suffering during this process, including pigs screaming, gasping, thrashing, and convulsing before collapsing in steel cages. As a result, more than 100 US veterinarians have joined in a letter to the American Veterinary Medical Association, expressing concerns about pigs’ aversive reaction to the gas.

Moreover, renowned animal scientist Dr. Temple Grandin has long called for the use of video cameras to observe pigs while they are being stunned or killed with CO2 gas.

Currently, US government inspectors are unable to determine whether pork-producing slaughter plants using CO2 gas are complying with the federal Humane Methods of Slaughter Act (HMSA) because—unlike with pre-slaughter stunning by electric current or captive bolt—inspectors are unable to observe animals after they are lowered into the CO2 chamber.

“Inexplicably, the use of CO2 gas appears to be the only approved slaughter method that plant inspectors are not able to directly observe,” the petitioners wrote.

“Since pigs represent the largest percentage of mammals that fall under the HMSA, the USDA is failing to enforce the nation’s sole humane slaughter law for a large majority of the animals killed for food in our country,” said Zack Strong, senior attorney for the farmed animal program at the Animal Welfare Institute. “By granting our petition, the department will be able to determine if it has been missing a significant number of humane slaughter violations by not observing CO2 stunning.”

In preparation for slaughter, pigs are typically driven into a gondola and exposed to increasing concentrations of CO2 as they descend to the bottom of a pit. The process can take several minutes, and multiple factors affect how long it takes for the animal to lose consciousness, including the specific concentration of CO2, the speed of the conveyor, and a pig’s age, sex, and genetics.

The HMSA mandates that all animals be rendered insensible to pain by a method that is rapid and effective before being shackled, hoisted, or cut. CO2-specific regulations under the law require that animals “be exposed to the carbon dioxide gas in a way that will accomplish the anesthesia quickly and calmly, with a minimum of excitement and discomfort to the animals.”

Further, the Federal Meat Inspection Act (FMIA) mandates that inspectors make “an examination and inspection of the method” by which livestock are slaughtered.

The coalition’s petition argues that requiring cameras is not optional for the USDA, as the department is unable to meet its legal obligation to administer the HMSA and FMIA without a way to observe animals within all stunning systems.

“The USDA is not allowed to take a ‘see no evil’ position regarding the slaughter of pigs; the agency has a duty to ensure each animal is stunned and slaughtered in accordance with the HMSA, and they obviously can’t do that if their inspectors are unable to observe this process,” said Gillian Lyons, director of regulatory affairs for Humane Society Legislative Fund.

Over the past two decades, the pork industry worldwide has transitioned from pre-slaughter stunning by electric current to stunning or killing with CO2 gas; electrocution is still used by many small pig slaughter establishments, along with captive bolt guns and firearms.

At least 32 pig slaughter facilities across the country—most classified as large—use CO2, according to USDA enforcement records. Iowa ranks first in the number of slaughter plants using CO2 stunning (at least eight), followed by Minnesota (at least four), and California and Illinois (at least three each).

Most large meat slaughter plants in the United have already installed cameras in many areas of their establishments—and videos from these cameras are sometimes shared with inspection personnel to determine if a humane violation has occurred. There is no evidence from enforcement records, however, that video is currently available from inside CO2 stunning areas.

“Compassion in World Farming urges the USDA to require video monitoring inside CO2 stunning areas to ensure pigs are rendered insensible quickly—and humanely—before slaughter in accordance with the Humane Methods of Slaughter Act,” said Dr. Hillary Dalton, senior research manager at Compassion in World Farming. “CIWF is also calling upon governments and industry to address all instances of extreme pig suffering at slaughter and adopt more humane slaughter practices as a matter of urgency.”

Several other countries require video monitoring of CO2 gas slaughter systems, including England, Scotland, Spain, and Israel.

“The factory farming industry hides behind closed doors, preventing regulators and the public from seeing the suffering and pain inflicted on the animals,” said Lindsay Oliver, executive director for World Animal Protection. “This petition will help shed some much-needed light on the harsh reality of pigs subjected to CO2 stunning and hold accountable any companies failing to comply with animal protection laws, limited as they may be. Improving oversight and transparency is a crucial step toward protecting pigs from cruelty.”

Media Contact Information

Marjorie Fishman, Animal Welfare Institute
[email protected], (202) 446-2128

Madison Longenecker, Compassion in World Farming
[email protected], (631) 710-8224

Madeline Bove, the Humane Society of the United States
[email protected], (213) 248-1548

Jeanne Turkheimer, World Animal Protection
[email protected], (646) 783-2210

The Animal Welfare Institute ( is a nonprofit charitable organization founded in 1951 and dedicated to reducing animal suffering caused by people. AWI engages policymakers, scientists, industry, and the public to achieve better treatment of animals everywhere—in the laboratory, on the farm, in commerce, at home, and in the wild. Follow us on Facebook, Twitter, and Instagram for updates and other important animal protection news.

Compassion in World Farming is a global farmed animal protection organization that campaigns peacefully to end factory farming and transition to a food system that is compassionate, fair, and sustainable for all. The charity works tirelessly towards a better future for animals, people, and the planet by educating concerned consumers and supporting meaningful public policy. With headquarters in the UK, we have representatives to support in Europe, the US, the Asia-Pacific Region and South Africa. To find out more about Compassion in World Farming or join the movement, visit: and follow us on TwitterInstagramTikTok and Facebook. 

We fight the big fights to end suffering for all animals. Together with millions of supporters, the Humane Society of the United States takes on puppy mills, factory farms, the fur trade, trophy hunting, animal cosmetics testing, and other cruel industries. Through our rescue, response and sanctuary work, as well as other direct services, we help thousands of animals in need every year. We fight all forms of animal cruelty to achieve the vision behind our name: a humane society.

Humane Society Legislative Fund works to pass animal protection laws at the state and federal level, to educate the public about animal protection issues, and support humane candidates for office. Formed in 2004, HSLF is incorporated under section 501(c)(4) of the Internal Revenue Code as a separate lobbying affiliate of the Humane Society of the United States.

The Humane Society Veterinary Medical Association (HSVMA) is a professional veterinary association with a focus on animal welfare. HSVMA uses its expertise and resources to advance animal welfare via leadership, advocacy, education, and service.

World Animal Protection is a global organization working to end factory farming and wildlife exploitation. They expose cruel systems, promote animal-friendly alternatives, and influence policy change. For over 70 years, World Animal Protection has been rewriting the story for animals. Working across almost 50 countries with offices in 12, World Animal Protection is the only animal welfare organization with UN Consultative Status, enabling the organization to engage with and influence global decision-makers. They prioritize animals in farming and wild animals exploited for use in entertainment, as pets, and in fashion.