Nearly every week it seems like there’s a new vape product on the market. Even though dried cannabis flowers are still the most popular purchase among California medical marijuana patients, according to the 2016 State of Cannabis report from weed delivery service Eaze, vapes are swiftly catching up.

Whereas in 2015, vaporizer cartridges only comprised six percent of Eaze’s total sales, in just a year they saw a 400 percent increase, climbing to 24 percent of sales among their 250,000 customers in 2016. Flower, on the other hand, dropped from 75 percent of total sales to 54 percent within the same time frame.

As more states decide to legalize adult use or medical marijuana, cannabis is becoming more accessible to a broader range of people, and gaining mainstream appeal. For new patients or novice users who can’t roll a joint, don’t want the mess of grinding up bud, or would rather not smell like weed, vaping offers a convenient, discreet, and tidy alternative.

“The people coming in to try cannabis now are new to the market; these aren’t your ‘stoners’ of the past,” says Jamie Feaster, founding team member and vice president of marketing at Eaze. “These are people who are curious about alternative forms of relief: working professionals, baby boomers, mothers, and so on.”

Related: Here’s What Fake Weed Vape Cartridges Actually Look Like

The new, non-traditional cannabis user is leading companies to change the rhetoric around these products. “The vapes we see that people are responding well to are the ones that focus on the effects,” says Feaster. Whereas for the seasoned stoner, words like “indica,” “sativa,” “hybrid,” and strain names actually mean something, newer consumers want a product’s name to describe how it makes them feel, he says. “People prefer products that are called things like ‘Relax,’ things like ‘Active,’ things like ‘Inspire.’ We’re starting to see these products and brands market themselves more around the experience, and less around the ingredients.”

However, the more a product’s branding deviates from what the substance actually is, the more obscure a vape pen’s ingredients become to the user. For instance, understanding that a pre-filled vape pen called “Relax” is actually a battery and ceramic cartridge, heated up to 400 degrees to activate an indica concentrate from Northern California with added terpenes (aromatic molecules), helps the user be more informed about about what they’re putting in their body.

Vaping might be convenient, but that’s the catch: few consumers have any idea what they’re actually vaping, what chemicals are mixed in with the cannabis oil, and what materials comprise the actual hardware. The vaporizer supply chain is fairly opaque, and the average person has little way to verify that what they’re inhaling is safe to consume.

Most vape brands purchase their hardware straight from China, or they cruise a trade site like Alibaba and buy the cartridges there, says Adam Lustig, CEO of Higher Vision Cannabis, which makes concentrates. “You punch in just about anything and get it directly from a factory in China,” he says.

Lustig’s company sells concentrate on its own, rather than in pre-filled cartridges. “I have a problem selling something I didn’t make,” he says, “until we find one that we can really put ourselves behind.”

He recommends cartridges with a ceramic core and made from stainless steel. “I look for the flavor—a coil that transmits the flavor of our oil the best. That’s number one,” says Lustig. “Number two is easy use, convenience, whether it leaks or not. Leaks happen. Under certain circumstances, in a hot car, at a certain angle, anything will leak. Then, there are some that are cheaply made, or break too easily.”

It’s also important to look out for plastic and low-grade wire, both of which can be dangerous and unhealthy to vape, he says.

Many of the factories that source vape cartridges also service the e-cigarette world, says Roger Volodarsky, CEO of Puffco, a load-your-own vaporizer company. Because e-cigarette liquid is less viscous than cannabis oil, manufacturers use cutting agents to thin out the concentrate so that it can be vaped in certain hardware, he explains. Unfortunately most of what’s used to thin out cannabis oil isn’t particularly healthy.

Some manufacturers use polyethylene glycol, or PEG. PEGs can be contaminated with ethylene oxide, which the International Agency for Research on Cancer classifies as a carcinogen. It can also harm the nervous system, and is classified as a “developmental toxicant” by the California Environmental Protection Agency. Other manufacturers use propylene glycol (PG), a common household solvent also used in deodorant sticks, hand sanitizers, cigar humidors, and smoke machines. In adverse reactions, a consumer can experience sore throat, muscle pain, or strong smelling urine.

“Instead of using propylene glycol, there was a shift to start using terpenes,” Volodarsky continues. The market considered terpenes to be safer than PEG or PG, since cannabis itself is already full of terpenes, he says. “But the problem [with] the terpenes included in cartridges is that few companies get them from cannabis. The rest are just buying terpenes that you get off Amazon as a cleaning solution, like [citrus terpene solvent] D-limonene.”

When purchasing a pre-filled vaporizer, there’s always going to be some sort of additive in it, Volodarsky says. “The convenience is really liberating. You can just hit it without loading it or touching it, but it doesn’t come without compromise.” Vapes lack the full spectrum cannabinoid effect that you get when smoking actual plant material, he says. Making a concentrate using either carbon dioxide or butane solvent, while manipulating the cannabinoid and terpene profile, weakens the integrity of marijuana’s natural entourage effect — the synergistic relationship which occurs among its various chemical components.

“If you’re buying a pre-filled vaporizer, make sure the information on the cannabis inside it is listed on the outside packaging,” says Volodarsky. Consumers should know the processes used to make the concentrate and if it’s been tested for pesticides. “I want prefill that only came from the cannabis plant; there aren’t a lot of market options available that do that,” he says. “That’s why I load my own vape.” Loading your own is a way to ensure that no additives are in the vape cartridge.

“There’s no regulation on actual vape cartridges. They have plastic burning and other shit outside the hash that’s inside them. The cartridges themselves can be hazardous,” says Doug Hitman, owner and founder of Chalice Festival, Happy Place Festival, and Hitman Glass. At the latest Happy Place Festival, a New Year’s cannabis, art, and glass festival outside Los Angeles, Hitman says that 80 percent of vape pens tested for pesticides failed. “The reason why is that to make a vape cartridge, you [use] a much lower grade hash oil. You would take the bottom of the barrel shit and put it in vape pens, because there’s a misconception that [vapes] clean up bad material.” He says what’s called “crude oil” is often loaded into cartridges by vape companies, going for between $3 and $8 per gram in California. “It’s the shit that people wouldn’t sell as hash oil by itself,” says Hitman.

In a recent investigation into cannabis oil, 44 products were tested for 16 different pesticides at Steep Hill Labs in Berkeley, California. The lab found that 41 out of the 44 products (or 93 percent of them) tested positive for pesticides at high enough quantities that certain states which regulate pesticides in cannabis products would ban them. “There are no failing levels in California [because] there are no regulations,” explains Reggie Gaudino, vice president of scientific operations and director of intellectual property at Steep Hill. Only the city of Berkeley has a cap on total pesticides at 100 parts per billion—far stricter than statewide regulations in Oregon or Colorado, which have various multi-hundred part-per-billion caps on individual pesticides applied to cannabis.

In the manufacturing process, pesticides might also concentrate at higher rates than cannabinoids: for example, a cannabinoid like THC might concentrate fourfold, but a pesticide could concentrate twentyfold. With the trade-off of compact, potent, and inconspicuous THC comes an elevated risk of inhaling less appetizing chemicals. “The entire industry has to look to the right standard to build, and stop thinking of ourselves as, ‘Oh we’re the underground, everything is cool, we can just grow bud in the basement and sell it,” Gaudino says. “If you want [cannabis] to be legitimate and a medicine, we have to start thinking like pharmaceutical companies do and grow our medical supply in a manner that is in accordance with medical use.” That means not drenching the bud in toxic chemicals that could make sick patients sicker.

“There’s not a ton of transparency in the [vaporizer] processes right now,” says Aaron Justis, CEO of the LA-based Buds & Roses dispensary. But as the industry evolves, he says, people will start to demand higher quality products. And with more competition, those that aren’t transparent about their processes, or who vend cheaply-made products, may ultimately get weeded out. Regulation due to debut in 2018 in California may also yield opportunities for legislators to hold vape companies accountable for the quality and safety of their products.

“It will change in the future, once they’re lab tested and regulated. I would say the more pure the oil is, the better,” says Justis. “That’s what people want right now. Vape pens are a growing part of the industry; it’s not going away.”