Vaping might be killing people. Hundreds of people across the country are falling ill with mysterious lung conditions, and four vape users have died after showing up to hospitals complaining of shortness of breath. Doctors aren't sure what is happening, and public-health officials are starting to call it an epidemic.

Cannabis vaping, which involves using a battery to heat a cartridge of pot oil to create an inhalable vapor, has exploded in popularity since legalization. So how freaked out should we be about these deaths?

Two cannabis health professionals I reached out to said that while the reports are concerning, they're not ready to tell their patients to stop vaping weed. Dr. David Knox, a physician with 40 years of emergency-room experience who now works in a private cannabis medicine practice in Oregon, told me that he doesn't recommend people start vaping, but he also isn't telling existing users to quit.

"I'm not worried to the level that I tell them to quit. I just want them to be aware that it is a risk," Knox said. "But if you've been vaping for quite a while and you have not been having any problem, [this health scare] doesn't mandate that you quit right now. But you do want to be cognizant of who is making your product, where it is from, and what its constituents are."

Knox said his first preference is for patients to use tinctures or topicals and avoid inhaling of any kind: "I've been telling folks for years that it's a new enough technology that we still don't know if it's going to give you some long-term problems."

Alison Draisin, a licensed mental health care provider at Seattle's AIMS Institute, said she often recommends vaping for people with anxiety and pain due to the "immediate relief of inhaling cannabis," and has not stopped after the recent health scare. She said she strictly recommends brands like Puffin Farm, Olala, and Heylo Extracts that do not dilute the cartridges with other chemicals.

"Less scrupulous processors may use cutting agents... and that is why it's important for stores and consumers to really know what they are purchasing and putting in their lungs," Draisin said.

The vast majority of these illnesses are being reported in states without legal cannabis, which may not be a coincidence. On the black market, no one is regulating what kinds of chemicals end up in your cartridge. If you're buying your vape cartridge from a legal store in Washington State, legally its contents should have been tested. Nevertheless, Draisin's advice is still to buy cartridges only from companies that use additive-free oil.

Brands like Puffin Farm, Olala, and Heylo Extracts use the same CO2 extraction equipment that pharmaceutical companies use, because CO2 is harmless to humans and any residual CO2 naturally evaporates as soon as the cannabis oil leaves its extraction machine. Cheaper solvents like butane are toxic to humans and can easily be left in the cartridge oil, which may be causing some of these illnesses.

Other flavorings or additives could also be causing the health scare. Weird chemicals like diacetyl or vitamin E oil have been found in black market vape pens and are known to be toxic. Other agents like propylene glycol can break down to dangerous chemicals like formaldehyde.

Do you want to inhale the vapor of formaldehyde, the same chemical used to embalm dead people? I'll answer that for you: No, you don't. So if you're in the habit of using vape pens, it's time to be more discerning about what cartridge you load into it.

Correction: An earlier version of this article misstated that the Cold Smoke brand uses CO2 extraction equipment. They do not.