As millions of Americans adopted mask-wearing this year to stop the spread of the novel coronavirus, they confronted a wild West of options, including artisanal products sold on Etsy, cotton coverings sewn by their family members and mass-produced items marketed by favorite retailers.

The personal protective equipment industry is trying to inject some clarity into the mask-purchasing experience by creating a uniform set of standards to show consumers how well the products would protect them and those around them.

But the industry players first have to overcome fierce disagreements among themselves, a rift that has delayed a process that is supposed to help businesses and schools reopen in 2021.

Company executives and scientists have spent months on the painstaking effort, which has been rife with squabbling over how much protection they can and should promise, among other issues. And it’s unclear whether the federal government plans to bless any new standards, potentially scaring companies away from making any significant upgrades.

“This has been a nightmare,” said Jeffrey Stull, president of International Personnel Protection, who is organizing the group’s discussions on a volunteer basis. “We really see a whole spectrum. Some individuals say we need a standard, we need to get that standard out, let’s make it a bit more lenient. … And then we have some people who say, ‘No, this has to be absolutely right.’ ”

Even President Trump has expressed an opinion about the effectiveness of masks in recent days. In one of several barbed attacks aimed at Anthony S. Fauci on Monday, Trump slammed his top infectious-disease specialist’s use of a Washington Nationals mask, saying “it is not up to the high standards that he should be exposing.” Fauci has advocated for months that Americans wear masks to protect others and frequently wears a mask in line with Centers for Disease Control and Prevention recommendations.

The process was born out of the chaotic scramble that millions of Americans faced this spring, as they sought access to face coverings during the coronavirus’s rapid spread. There was an immediate shortage of surgical masks and the more protective respirator masks most often used by construction workers, so many people had to adapt by turning to amateur solutions.

Without access to special laboratory equipment, it’s nearly impossible for most people to know which masks are the most effective at stopping the spread of infectious particles.

Though the details can be mind-numbingly technical, the stakes are high: If widely adopted, the standards could give Americans a sense of certainty and perhaps more confidence to return to offices, classrooms and public spaces next year. Masks that meet the standards could give additional protection to essential workers who have been largely unable to access N95 respirators, given the ongoing shortage.

Industry players have had to wrestle over what that protection should look like: what size particles the masks should be tested against, whether and how to ensure masks fit properly, and what kind of third-party certification the standards should require.

These disputes are expected to come to a head in the coming weeks. By the end of this month, the working group hopes to send out a version of the standards to experts in protective clothing and equipment, most of whom have not been involved in crafting the language. They have a month to send in their ballots, which can include suggestions for changes.

This process is far faster than usual. The safety qualities of a variety of consumer products, including car seats and fireworks, are graded by either government agencies or industry groups as a way to set standards, inform consumers and keep companies honest. Those evaluations typically take more than a year to roll out. Rarely has there been the rapid growth of a product that has occurred in the mask market this year, and the diversity of products has been astounding, from “gaiters” worn around the neck to high-end masks made of silk or lace. Just in April, buyers purchased 12 million masks on Etsy.

“Whether it’s a standard or whether it’s something equivalent to the Consumer Reports rating (of) good, better or best, it is probably useful because otherwise people are lost,” said Philip Harber, a professor of public health at the University of Arizona who studies the use of respirators. He warned that given some Americans’ hostility toward masks, the standards have to be “very, very, very simple.”

The effort is being organized by ASTM International, formerly known as the American Society for Testing and Materials, which develops standards on a wide range of products, including amusement rides, cannabis devices and drones. ASTM is providing the platform for the group trying to hash out the rules, and its work would result in a voluntary standard that manufacturers can adhere to and advertise on their products.

The goal, said Erick Couch, who used to work in the aerospace industry and is trying to coordinate manufacturers for the effort, is that the Centers for Disease Control and Prevention would then recommend to Americans that they use masks made to the ASTM standards — thereby creating instant market demand. Couch is not formally affiliated with ASTM but has been in close touch with people in the working group.

“Companies won’t invest unless there’s demand that they can bet on,” Couch said. “What’s called for here is true leadership, and it can have immediate impact on reducing risk and helping the economy go roaring back because finally those of us who want to wear masks can have something that we can be confident will protect us.”

The new mask standards are being discussed by a group of about 50 scientists, industrial hygienists, government officials, special interest groups and manufacturers, some of whom stand to profit off the sale of the resulting masks. Employees from 3M, Honeywell, ExxonMobil’s chemical unit and DuPont have been involved in the discussions.

Standards for a mask for the general public fall into a regulatory gray area. The CDC’s National Institute for Occupational Safety and Health certifies respirators used in occupational settings, and the Food and Drug Administration regulates masks intended for medical purposes.

A CDC spokeswoman did not respond to questions, including whether the agency would consider encouraging the public to wear masks that adhere to the new standards.

The FDA has not been involved in the ASTM effort, but depending on how manufacturers market their masks and their claims of disease prevention, they may be required to submit testing data to the agency to verify their claims, an FDA official said.

The process to nail down the standards has been marked by intense disagreements among working group members. The hours-long Zoom calls to decide what the standards will look like have resembled “cats and dogs fighting,” said Dave Rousse, the president of INDA, a trade association for the nonwoven fabrics industry.

One of the major points of contention goes to the heart of how confident people should feel when they put on one of these masks and how manufacturers can market them. Someone wearing a surgical or fabric mask is mainly protecting others, as the CDC has asked Americans to do. People wearing a product qualifying as a respirator are going a step further and protecting themselves.

Some members of the working group “think we should be able to assert that, even if these aren’t respirators, they offer a degree of respiratory protection,” Stull said.

At the moment, the group is contemplating two classifications within the new standards — one for face coverings that filter out between 20 and 50 percent of small particles and another for face coverings that are shown to filter out more than half. They would be tested using particles of the same size that are used to test N95 respirators, Stull said.

Others worry that advertising any level of respiratory protection for a non-respirator — even if the products are far more effective than a regular fabric mask — would offer Americans a false sense of safety.

“We have warnings in the standard that will say, ‘This is not a respirator,’ ” Stull said. “That will be on the packaging. Some people say it needs to be printed on the product itself.”

ISEA, the International Safety Equipment Association, also makes standards for protective equipment. When construction workers choose a hard hat, for example, they can read the label and know that it will offer them a certain level of protection.

“It’s exactly that level of clarity, transparency, understanding and predictive performance that can be provided for these barrier masks in the future,” ISEA President Charles Johnson said. “Is this thing protecting me? How much is it protecting me? How does it compare to this other product? Those are the questions the standards are designed to answer.”

But the ISEA, whose members include major N95 manufacturers 3M and Honeywell, has decided that creating standards that promise protection to both the wearer and people around the wearer would be impossible to do in a responsible and timely manner.

Instead, the ISEA is attempting to develop its own standard, which would ensure only that the wearer was meeting CDC guidance by not contaminating the air around them — a process the industry calls “source control.” But with multiple standards comes the risk of confusing consumers.

So, too, could the multiple numbers and ratings that may appear on the packaging of the resulting masks. One major debate among ASTM members has been whether the new standards should advertise a face covering’s effectiveness in filtering out both large and small particles, effectively providing two numbers for consumers to judge. Small and large particles are generated when people talk, breathe, sneeze or cough.

Advertising the effectiveness against just larger particles may give people false confidence in their face covering, while only providing the effectiveness against smaller particles may make the products less appealing.

The ASTM working group has also argued over how much manufacturers can be trusted. Many say that an outside entity, such as an accredited laboratory, should be required to verify that masks meet the standards. But this could create bottlenecks and increase the cost of the final product.

The laboratories that would profit off such a requirement are also a part of the working group, along with the manufacturers who would benefit from a more lax arrangement.

The group has landed on a “hybrid solution” for now, Stull said: Accredited laboratories will have to sign off on the masks’ filtration and airflow resistance, which is a measure of how hard it is to breathe through. All other criteria mentioned in the new standards — labeling, design, user instructions and so on — will be self-declared by the manufacturer.

Ensuring the masks fit people properly has also been a major debate in the ASTM discussions, participants said. For decades, scientists and manufacturers have been trying to make masks that form a tight seal to the face; N95s are designed to do so, which is why they can be so uncomfortable.

For now, the ASTM group has decided on an optional fit test, to be carried out by manufacturers rather than a laboratory, using a panel of people with “a range of different face sizes,” Stull said. But because the assessment will be done on test subjects rather than each individual wearer, it can provide only a general estimate of how well the masks fit, he said.

Compromising on fit is yet another example of how the experts and companies have had to balance competing priorities — making the most effective mask possible, while making it practical for millions of Americans to use every day.

If these issues are resolved, by early 2021, masks on store shelves may be marketed with a promise of a certain level of protection for the wearer, akin to “N40s,” “N60s” or “N80s.”

“We are grappling with these issues, which, for a very simple product, have been considerably more complex than we ever imagined,” Stull said. “It’s hard to do all this, but ultimately we’re going to come out with a good standard.”