Glovebags Versus Critical Barriers

The question that comes up frequently in asbestos training classes is whether a glovebag fulfills the critical barrier requirements of OSHA or not. Glovebag means not more than a 60 × 60 inch impervious plastic bag-like enclosure affixed around an asbestos-containing material, with glove-like appendages through which material and tools may be handled. The definition of a critical barrier is one or more layers of plastic sealed over all openings into a work area, or any other similarly place physical barriers sufficient to prevent airborne asbestos in a work area from migrating to an adjacent area.

Distinction Between Glovebag and Critical Barrier

The preamble to the OSHA Asbestos Standard in 1994 gives us some background information. They say that Class I work such as the removal of TSI or friable surfacing ACM or PACM must be performed using procedures in paragraph (g)(4) and using a control method which is listed in paragraph (g)(5). Critical barriers are a (g)(4) procedure, glovebags are a (g)(5) control method. This is an important distinction. If another control method is used, or if a listed control method is modified, the standard in paragraph (g)(6) requires that a certified industrial hygienist (CIH) or licensed professional engineer who is a project designer certify the control method using the criteria set out in the regulatory text. 

OSHA Requirements

The requirements of (g)(4) are: for Class I jobs, preparation must be supervised by a competent person, dropcloths must be used, and HVAC systems must be isolated. The area must be set up using critical barriers, either as part of a negative pressure enclosure system or as a supplemental barrier to another listed system, which isolates the asbestos disturbance in a different way. Other barriers or isolation methods may be used to prevent asbestos migration. The effectiveness of such methods must be proven by visual inspection and clearance or perimeter monitoring. OSHA believes that the size of the removal job alone does not predict the risk to workers. However, if a job is smaller there is less chance that isolation barriers provided by glovebags or gloveboxes will fail. This refers to the requirement that additional critical barriers are only required for glovebag projects over 25 linear feet. 

Continuing with the preamble, OSHA was reluctant to limit glovebag removals without critical barriers only to maintenance projects where, as NIOSH noted, it is more likely that crews will be untrained. Rather, OSHA has followed the lead of some states which allow removals involving fewer than 25 linear feet of TSI or 10 square feet of other material to be handled without critical barriers, unless the glovebags or enclosures lose their integrity, or where a negative exposure assessment has not been produced. 

Critical barriers are required in addition to glovebags for projects less than 25 linear feet if there is no negative exposure assessment. Such projects are Class I removals. Workers who perform them must be trained in an EPA accredited training course or equivalent. OSHA believes that the workforce performing these relatively minor removals is the same workforce performing major removals. Thus, the job will be well conducted and critical barriers will be unnecessary. In addition, where the employer cannot demonstrate that a Class I job is unlikely to over-expose employees, the employer must ventilate the regulated area to remove contaminated air from the employees’ breathing zones.

Control Methods

Continuing with the language of the OSHA preamble to the asbestos standard, paragraph (g)(5) lists control methods that OSHA evaluated during this rulemaking. The agency finds that using these methods pursuant to the limitations and specifications in the paragraph is likely to effectively control employee exposures when performing Class I work. 

The first control system listed for Class I work is the Negative Pressure Enclosure System, or NPE. The extent to which OSHA should require these systems for major asbestos work was a remanded issue. OSHA has found that NPEs, when constructed and used according to the criteria in the standard, can effectively protect employees within and outside the enclosure. 

Other listed systems may be used for Class I work under stated limitations. Paragraph (g)(5) sets out these limitations. These systems are: glovebag systems, negative pressure glovebag systems, negative pressure glovebox systems, the water spray process system, and a mini-enclosure system. OSHA emphasizes the use of the term "system". Each method consists of tangible materials and devices, and procedures and practices. All the listed elements must be complied with before OSHA's finding of effectiveness is relevant. Other unspecified control methods — or "alternative control methods" – may be used if additional notification is given to OSHA, and if a specially trained project designer or CIH certifies that the controls will be protective. 

Class I Work

Class I work i.e., the removal of TSI and/or surfacing ACM or PACM must be performed using procedures in paragraph (g)(4) and using a control method which is listed in paragraph (g)(5) of the standard. If another control method is used, or the listed control method is modified, the standard paragraph (g)(6) requires that a certified industrial hygienist (CIH) or licensed professional engineer who is a project designer certify the control method using the criteria set out in the regulatory text. 


The takeaway from all of this is that if you have a glovebag job that is Class I, and the job is more than one glovebag, which is 60 inches by 60 inches as specified for Class III, and you're less than 25 linear feet or 10 square feet, OSHA does not require critical barriers unless you don't have a negative exposure assessment. Above 25 linear feet for glovebag projects or 10 square feet, the standard requires that even if you have glovebags, you must have critical barriers. If there is not a feasible way in OSHA language to put up these critical barriers, then the standard requires perimeter monitoring, with each barrier monitored with a PCM sample with results back within 24 hours and the results showing you're below the clearance levels or are below background levels. But above 25 linear feet, glovebags have to be supplemented by critical barriers or their equivalent, whether or not you have a negative exposure assessment.

CDC's New Lead Poisoning Resources

The CDC recently put up on their website two new videos designed to educate the public about the dangers of childhood lead exposure. The first video, “Childhood Lead Poisoning Prevention,” is written for a general audience. The second video, “Childhood Lead Exposure Prevention Education,” is for high schoolers.

Lead and Lead Poisoning

A naturally occurring metal, lead has been used in a wide variety of consumer and industrial products. Lead poisoning can cause health problems in people of any age, but children under the age of 6 are most vulnerable. Despite long-standing bans on lead paint and leaded gas, lead exposure remains a common hazard.

Overview of Lead Exposure

The two CDC videos overlap on many of the topics they cover. Both videos provide an overview of what lead is. Both describe how lead exposure happens. Lead paint and pipes, contaminated spices and cosmetics, and battery and ammunition manufacturing are some of the sources of lead exposure.

Health Effects and Lead Safety

Both videos discuss the health effects of lead poisoning. At high doses, lead poisoning can be fatal. More typically, smaller doses of lead can result in developmental delays in children and behavioral problems in teens and adults. Also, the two videos also discuss lead-safe behaviors. Performing these actions helps avoid or minimize lead exposure.

Homeowners and Parents

The first video covers requirements for landlords and home sellers to disclose the presence of lead in housing. And it has resources for parents, including services that help children exposed to lead. While the second video, written for a high school audience, spends more time on the sources of lead exposure, particularly those in the home, and lead-safe behaviors that reduce the risk of lead poisoning.

Additional Resources

To learn more about lead poisoning, its health effects, how to minimize exposure and how doctor’s test for it, visit the CDC’s Childhood Lead Poisoning Prevention website

Further Reading

The EPA Updates Lead Training

The Flint Water Crisis

Explosion at a Chocolate Factory

In March, an explosion at a chocolate factory in Pennsylvania killed seven people and wounded at least 10 others. Some workers said they smelled natural gas prior to the explosion at R.M. Palmer Co. 

Survivor landed in chocolate tank

One of the survivors, an employee named Patricia Borges, fell through into a vat of chocolate when the floor collapsed from the blast. She broke a collar bone and both heels, but the liquid chocolate put out the flames burning her arm. She waited 9 hours to be rescued. 

Borges thinks the factory should have evacuated after workers complained of the gas odor. The National Transportation and Safety Board (NTSB) has called the accident a natural gas explosion. But an official cause has yet to be determined. The NTSB is the lead on the investigation. Though other agencies, including OSHA, are investigating as well.

R.M. Palmer posted on their Facebook page that they are devastated by the tragedy and are cooperating with the investigation.

Explosive hazards in manufacturing

Unfortunately, explosions are a common hazard in manufacturing, including in food manufacturing. Commercial ovens and furnaces often run on natural gas. And powdered ingredients can create combustible dusts.  Cocoa powder and starch, both used in the manufacture of chocolate candy, are explosive hazards. It is possible that combustible dusts contributed to the Palmer factory blast.

Previous accidents at Palmer

OSHA fined R.M. Palmer $13,000 in 2018 when an employee lost a finger tip. They were cleaning a pressurized valve at the time of the accident. In 2019, the company paid OSHA $26,000 because a conveyor belt broke an employee’s arm. This past January, OSHA fined them $12,000 for an undisclosed incident.

Another chocolate factory accident

In a previous META blog, we discussed a separate incident at a Mars Wrigley factory. Two workers fell into a tank partially filled with chocolate. Rescuers cut into the vat to rescue the workers. OSHA cited Mars for not providing the workers with proper procedures on isolating flowable hazards.

Factory explosion survivor, on fire, fell into chocolate vat

R.M. Palmer Company releases statement

Deadly chocolate factory blast highlights combustion risks

Respirator Fit Evaluation Challenge

The National Institute for Occupational Safety and Health (NIOSH) has organized a Respirator Fit Evaluation Challenge. The goal of this crowdsourcing competition is to find new ways to improve respirator fit testing. There is $350,000 in total prize money.

Concept Paper

To participate in the first phase of the competition, individuals or companies must submit by May 1 a concept paper that describes how to improve fit testing. Up to 20 of these papers could win $5,000 and be invited to continue to Phase 2 of the competition.

The Reason for the Competition

People and respirators come in a variety of shapes and sizes. Given the wide use of respirators and sporadic fit testing, it is important to find easier and more immediate ways for people to get feedback on whether their respirator is correctly fitted and working properly. This is the reason for the NIOSH competition.

How to Enter

Click here to visit the Respirator Fit Evaluation Challenge home page and learn more about the competition, including how to enter.

Click here to read the press release for the challenge.

Workers Fall Into Chocolate Tank

The Occupational Safety and Health Administration issued a serious citation and fine to the Mars Wrigley corporation after two workers fell in a tank used to manufacture chocolate. Emergency responders had to cut a hole in the bottom of the tank to free the workers. And both were taken to the hospital, one by helicopter.

Outside Contractors

The two workers were not employees of Mars Wrigley. Rather, they were outside contractors performing maintenance work on a vat used to make Dove chocolate. The tank was partially filled with chocolate at the time of the accident. 

OSHA Violations

The OSHA Violation Detail states that one of Mars Wrigley’s own employees was involved with “the control of hazardous energy” in the tank. And that the company failed to ensure that that employee understood “the type and magnitude of the energy for the task.” 

Additionally, entry into the tank is permitted. The two outside employees needed to verify that any flowable material in the tank was isolated prior to entry. The chocolate manufacturer failed to provide the two contractors, who were cleaning the vat, “with the correct energy control procedure or work authorization permit” required to safely enter and work in the tank.

Isolating Flowable Hazards

The techniques used to isolate confined spaces with flowable hazards are found in paragraph (b) of 29 CFR 1910.146. These techniques are blanking or blinding; misaligning or removing sections of lines or pipes; or a double block and bleed system.

Mars Fined

This incident at the Mars Wrigley plant occurred in June of 2022. After an investigation, OSHA levied a fine of $14,500 in December.

Stay Safe Through the Holidays

We are well into the holiday season. For many, this is a wonderful time when families and friends get together and enjoy each other’s company. But holidays can also be busy and stressful, which might lead to being hurried and careless. And this means more accidents. We want you to have a safe and fun time. So here are some helpful tips to stay healthy and safe this winter.


Traveling by car during the holidays is more dangerous than at any other time of the year. You can expect heavier traffic and impatient drivers. Make sure your car is ready for the road. This includes anything you might need if you run into bad weather. Drivers should get plenty of rest before getting behind the wheel and avoid using the phone while driving. And everyone in the car should wear a seatbelt. Since many car accidents involve alcohol, a sober driver helps everyone get home safely.


Decorating is an important part of the season. If you are putting up an artificial tree, check that it is fire resistant. Water live trees to prevent them from drying out. Keep all trees away from sources of heat. Place ornaments that are breakable or made up of small pieces higher up the tree, away from children. Be careful with candles. Don’t place them near flammable objects or within reach of kids. Candles should not be unattended. Strands of lights should be in good shape. Don’t nail or staple through the wire. And don’t plug more than three strands together in a row. Turn off all decorations when you leave the house or go to bed.


Food poisoning sends people to the emergency room every day. Wash hands frequently when preparing and handling food. Keep uncooked meats away from cooked food and fresh fruits and vegetables. This means using separate utensils and cutting boards. Use a food thermometer to cook meats to a safe temperature. And refrigerate leftovers within two hours after the food was served.


Gift safely! Toys for younger children have age-ratings for safety. Buy toys with the correct age range for the recipient. For children under 3, choose toys that will not be a choking hazard. Avoid small balls and toys with buttons or magnets. For children under 10, toys that must be plugged in are risky. Riding toys, like bikes or scooters, should come with any necessary safety gear.

These are just a few tips to help you celebrate the holidays more safely. For more information, check the links below. We hope you have a wonderful and incident-free holiday season!

Sources and more information:

Tips from the National Safety Council

Holiday safety from the Consumer Product Safety Commission

Stay safe with the Red Cross

For more on safety, click here to visit META's blog page.