A months-long methane gas leak in Los Angeles is fouling the air and causing choking, stinging eyes, severe headaches and even nosebleeds among residents of the affected neighbourhoods, compelling California Governor Jerry Brown to finally declare a state of emergency.

It's one of the largest methane leaks in history, and it won't be stopped until February, or perhaps even March. Since October, some 80,000 metric tons of the toxic gas has seeped into the air from a breach in an underground storage tank for natural gas operated by the Southern California Gas Company. It's releasing the greenhouse gas equivalent of driving 7 million extra cars each day.

Citizens of the Porter Ranch community nearby in the north-west San Fernando Valley are being particularly affected by the noxious fumes, and many have fled their homes. Brown ordered that all state agencies "utilize all necessary state personnel, equipment, and facilities to ensure a continuous and thorough response to this incident."

The new state of emergency rules will now require stepped-up inspections and safety measures for all natural gas storage facilities in California. The regulations would also require operators of gas storage facilities to conduct daily inspections of wellheads using infrared leak-detection technology, verify the mechanical integrity of wells, measure gas flow and pressure and regularly test safety valves, among other steps, reports the Los Angeles Times.

As for current effects, Brown believes the utility company must pay for all damage as well as mitigate the impact of the methane by investing in projects to reduce other pollution. Each storage facility will also have to draft a risk management plan that would examine the corrosion potential of pipes and other safety threats.