Engineering Controls, Work Practices, and Exposure 

Monitoring for Occupational Exposures to Diacetyl and 

2,3-Pentanedione

BEST PRACTICES

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

BEST PRACTICES

Engineering Controls, Work Practices, and 

Exposure Monitoring for Occupational Exposures 

to Diacetyl and 2,3-Pentanedione

By Kevin H. Dunn, Lauralynn Taylor McKernan, and Alberto Garcia

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health
ii Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

This document is in the public domain and may be freely copied or reprinted.

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Web addresses referenced in this document were accessible as of the publication date.

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SUGGESTED CITATION

NIOSH [2015]. Best practices: engineering controls, work practices and exposure monitoring for occupational exposures to diacetyl and 2,3-pentanedione. By Dunn KH, McKernan 

LT, Garcia A. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS 

(NIOSH) Publication 2015-197.

DHHS (NIOSH) Publication No. 2015-197

July 2015

Safer • Healthier • PeopleTM
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione iii

ACKNOWLEDGMENTS

The principal contributors to this publication were Kevin H. Dunn and Alberto Garcia, Division of Applied Research and Technology; Lauralynn Taylor McKernan, Laura Hodson, Todd 

Niemeier, Vanessa B. Williams, Gino Fazio, Ellen Galloway, and Rachel Thieman, Education and 

Information Division; James Couch, Division of Surveillance, Hazard Evaluations and Field Studies; Richard Kanwal, John Whalen, Edward Burroughs (under contract to the National Institute 

for Occupational Safety and Health); and Greg Kullman, Division of Respiratory Disease Studies.

Prior to publication this document was reviewed by Kay Kreiss, Division of Respiratory 

Disease Studies. Technical expertise was provided by Ann Hubbs, Health Effects Laboratory 

Division; and Jay Parker, National Personal Protective Technology Laboratory. This document 

was also externally peer reviewed by Kelly Howard, California Occupational Safety and Health 

Administration (Cal/OSHA); and Gerry Lanham, KBD Technic.
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Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione v

CONTENTS

DESCRIPTION OF EXPOSURE AND HEALTH EFFECTS . . . . . . . . . . . . . . . . . . 1

ENVIRONMENTAL MONITORING FOR DIACETYL AND 

2,3-PENTANEDIONE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Sampling and Analysis for Diacetyl Vapor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Sampling and Analysis for 2,3-Pentanedione Vapor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Sampling and Analysis for Powders and Particulates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Real-time or Near Real-time Techniques for Diacetyl and 2,3-Pentanedione . . . . . . . . . 4

CONTROLLING EXPOSURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

ENGINEERING CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

General Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Ventilation Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

General Engineering Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Small-Scale Weighing and Handling of Flavoring Ingredients . . . . . . . . . . . . . . . . . . . . . . 7

Filling, Mixing, and Emptying of Large Mixing Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Dumping of Powdered Ingredients into a Blender (Bag Dumping) . . . . . . . . . . . . . . . . . . 9

Discharging of Powdered Flavoring from a Blender/Spray Dryer (Bag Filling) . . . . . . . . 9

ADMINISTRATIVE AND WORK PRACTICE CONTROLS . . . . . . . . . . . . . . . . . . . 10

PERSONAL PROTECTIVE EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

ADDITIONAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

LIST OF FIGURES

Figure 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 1

BEST PRACTICES

Engineering Controls, Work Practices, and 

Exposure Monitoring for Occupational Exposures 

to Diacetyl and 2,3-Pentanedione

Workers who handle diacetyl or work in areas where diacetyl exposure occurs are at risk 

of developing severe lung disease if their exposures are not properly controlled. The National 

Institute for Occupational Safety and Health (NIOSH) has developed guidance in a variety of 

areas to reduce workers’ exposures to diacetyl through engineering controls, best work practices, and techniques for monitoring airborne diacetyl exposures. Although these guidelines 

emphasize diacetyl, they can be applied to reduce exposures to diacetyl substitutes such as 

2,3-pentanedione and other alpha-diketones.

DESCRIPTION OF EXPOSURE AND HEALTH EFFECTS

Flavorings are substances that alter or enhance the taste of food. They are composed of various natural and manmade chemicals and may consist of a single chemical, but more often they 

are complex mixtures. Workers in the flavorings production industry may be exposed to these 

substances in the form of solids, liquids, or vapors. Although thousands of flavoring ingredients 

are in use, little is known about most of these in terms of worker health effects, and few have 

occupational exposure guidelines such as recommended exposure limits (REL), permissible 

exposure limits (PEL), or threshold limit values (TLV)®.

NIOSH investigations have found that workplace exposure to diacetyl can result in reduced 

lung function and also cause a severe lung disease known as obliterative bronchiolitis. In obliterative bronchiolitis, inflammation and scarring occur in the smallest airways of the lung and 

can lead to severe and disabling shortness of breath. Symptoms include cough and shortness of 

breath on exertion. Obliterative bronchiolitis is an irreversible lung disease whose symptoms 

typically do not improve when the worker goes home at the end of the workday, on weekends, 

or on vacations. Obliterative bronchiolitis can reduce lung function enough to cause disability.

Occurrences of obliterative bronchiolitis were observed in the microwave popcorn industry in 2000 when eight workers were diagnosed with the disease after exposure to vapors from 

artificial butter flavoring ingredients including diacetyl [Akpinar-Elci et al. 2004a; Kreiss et al. 

2002]. Several workers in flavoring manufacturing facilities were also diagnosed with obliterative bronchiolitis or severe fixed obstructive lung disease [CDC 2007]. Studies in four microwave popcorn plants found that a history of working as a mixer and higher cumulative exposure to diacetyl were associated with decreased lung function [Lockey et al. 2009]. In one 
2 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

flavoring manufacturing plant, nearly one third of workers had restrictive breathing abnormalities [NIOSH 2011a]. This suggests that workers exposed to diacetyl and other flavoring ingredients could potentially develop a range of occupational lung diseases.

More recently, facilities have begun producing or working with substitutes for diacetyl, such 

as 2,3-pentanedione [Day et al. 2011; Boylstein 2012]. 2,3-Pentanedione, a 5-carbon alphadiketone, is chemically very similar to diacetyl, a 4-carbon alpha-diketone. Reports on the 

toxicity of 2,3-pentanedione were first published in abstract form in 2010 [Hubbs et al. 2010; 

Morgan et al. 2010]. Acute inhalation exposures to 2,3-pentanedione cause airway epithelial 

damage that is similar to diacetyl in laboratory studies [Hubbs et al. 2012]. In 2-week inhalation studies in rats, 2,3-pentanedione caused proliferation of fibrous connective tissue in the 

walls of airways, and projections of fibrous connective tissue sometimes extended into the air 

passageways [Morgan et al. 2012a,b]. Preliminary data suggest that repeated exposures to either 2,3-pentanedione or diacetyl can cause airway fibrosis in rats [Morgan et al. 2012a]. In 

the acute inhalation study of 2,3-pentanedione, changes in gene expression were noted in the 

brain [Hubbs et al. 2012]. As a group, these results raise concerns that the toxicologic effects of 

diacetyl may be shared with other alpha-diketones, which are close structural analogs. Additional alpha-diketones of interest include but are not limited to those used in food manufacturing such as 2,3-hexanedione and 2,3-heptanedione. Diacetyl substitutes should not be assumed 

to be safe until toxicology studies are performed.

It is difficult to quantify the number of employees involved with flavor manufacturing and, 

more specifically, those who have diacetyl or diacetyl substitute exposure in the United States. 

According to the Environmental Protection Agency Non-Confidential Inventory Updating Report, diacetyl had an aggregate production volume between 10,000 and 500,000 pounds in 2002 

[EPA 2002]. The North American Industry Classification System (NAICS) category 311, the 

most relevant category, includes subcategories Flavoring Syrup and Concentrate Manufacturing 

(NAICS Code 311930), Spice and Extract Manufacturing (NAICS Code 311942) and All Other 

Miscellaneous Food Manufacturing (NAICS Code 311999). In 2002, 21,000 workers were employed in facilities classified under 311930 and 311942 [Department of Commerce 2004]. According to the Flavor Extract Manufacturers Association, whose members account for approximately 95% of all flavors produced in the United States, a total of 6,520 employees work directly 

in the flavor manufacturing or laboratory activities in membership companies [Hallagan 2010]. 

In addition to workers who were exposed to diacetyl during its production or addition to flavored substances, health effects have also been observed in workers with downstream exposure 

to diacetyl from those flavored substances, including workers in areas such as quality control 

and packaging products within microwave popcorn facilities [Kanwal et al. 2006].

In 2010, California promulgated a regulation for occupational exposure to food flavorings 

containing diacetyl that requires installation of exposure controls to reduce exposures to the 

lowest feasible levels. In 2012, the American Conference for Governmental Industrial Hygienists published a threshold limit value® of 0.010 parts per million (ppm) 8hr-time weighted average (TWA) with a short-term exposure limit (STEL) of 0.020 ppm for diacetyl [ACGIH 2012]. 

NIOSH published its draft recommended exposure limits for diacetyl (5 parts per billion [ppb] 

8hr-TWA, 25 ppb STEL) and 2,3-pentanedione (9.3 ppb 8-hr TWA, 31 ppb STEL) in August 

2011 [NIOSH 2011b].
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 3

ENVIRONMENTAL MONITORING FOR DIACETYL 

AND 2,3-PENTANEDIONE

Measuring workers’ exposures to diacetyl or 2,3-pentanedione may help: (1) identify processes, locations, or tasks with exposures of concern; (2) guide corrective actions such as engineering 

controls; (3) identify improved work practices; and (4) select appropriate respiratory protection. 

Diacetyl and 2,3-pentanedione are monitored using personal and area air samples because the 

predominant route of exposure is inhalation. Studies conducted by NIOSH researchers [NIOSH 

2008a,b,c] and Martyny et al. [Martyny et al. 2008] describe common tasks performed by workers 

in the production of flavorings. Results of these surveys illustrate how sampling can identify emission sources and guide corrective actions.

Personal breathing zone sampling is the preferred method for estimating the exposure of 

a worker. To collect a breathing zone sample, the Occupational Safety and Health Administration (OSHA) states that the air sampling collection media be attached “to the shirt collar or as 

close as practical to the nose and mouth of the employee’s breathing zone” [OSHA 2008a]. For 

personal sampling, a worker is outfitted with the air sampling equipment, and the inlet to the 

collection media is positioned within the worker’s breathing zone. Area sampling can be performed for several purposes such as to evaluate exposure characteristics associated with a work 

area or process or to determine the efficacy of control systems. While the same sampling equipment and analytical procedures may be used in some cases for personal and area sampling, 

area sample results represent air concentrations at a fixed location. In contrast, personal sample 

results represent worker exposure averaged over the selected sampling period. The development 

of a comprehensive sampling strategy to assure selection of representative employees, appropriate work areas and proper sampling periods (time-weighted average vs short-term exposure 

limit sampling, etc.) should be done in consultation with a qualified professional. Sampling for 

diacetyl and 2,3-pentanedione as a vapor and a particulate (when present) should be considered because these compounds may be found in both phases. 

SAMPLING AND ANALYSIS FOR DIACETYL VAPOR

Chemists at NIOSH and OSHA have developed a variety of sampling and analytical methods for determining concentrations of airborne diacetyl vapor. Selection of a method to use 

in any given situation should be made after consultation with an analytical laboratory accredited by the American Industrial Hygiene Association for analyses. Only qualified professionals 

should collect samples.

OSHA Method 1013 can be used simultaneously for diacetyl and acetoin [OSHA 2008b]. 

Samples are collected through two 600 mg tubes that contain specially cleaned and dried silica 

gel in series at 0.05 L/min for 180 minutes for a time-weighted average (TWA) concentration or 

0.2 L/min for 15 minutes for short-term concentration. Samples are extracted with an ethanol 

solution and analyzed by GC-FID.

OSHA Method 1012 is more sensitive and can also be used to analyze for diacetyl and acetoin for either a 180-minute or 15-minute sample [OSHA 2008c]. OSHA Method 1012 utilizes 

the same sample collection media and conditions as OSHA Method 1013. Prior to analysis, the 

extract is derivatized and analyzed by gas chromatography with electron capture detection to 

produce a tenfold increase in sensitivity.
4 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

SAMPLING AND ANALYSIS FOR 2,3-PENTANEDIONE VAPOR

OSHA Method 1016 can be used to measure 2,3-pentanedione concentrations [OSHA 

2010]. Samples are collected through two 600 mg tubes containing specially cleaned and dried 

silica gel in series at 0.05 L/min for 200 minutes for a TWA concentration or 0.2 L/min for 15 

minutes for short-term concentration. Samples are extracted with ethyl alcohol:water solution 

and analyzed by GC-FID.

SAMPLING AND ANALYSIS FOR POWDERS AND PARTICULATES

Sampling and analytical methods are available to quantify airborne particulate concentrations 

in the inhalable, thoracic, and/or respirable size ranges, but these methods are not specific for 

diacetyl or 2,3-pentanedione content. Measurement of airborne dust particles according to their 

size (e.g. inhalable, thoracic, and respirable) can help to inform where they may deposit in the 

respiratory tract. Several types of sampling devices are available (e.g., inhalable dust samplers, 

impactors, cyclones, and sampling cassettes) to provide measurements of different size fractions 

of airborne dust. In most cases, dust is collected onto a filter, and the filter can be analyzed gravimetrically to provide the mass of the dust. Validated methods such as NIOSH Method 0500 for 

total dust and NIOSH Method 0600 for respirable dust are available for the collection and gravimetric analysis of airborne dust [NIOSH 2012]. The collection filters should be hydrophobic (e.g., 

polyvinyl chloride) to minimize collection of moisture. Because of their toxicity, when a dust contains diacetyl and 2,3-pentanedione the results from this method should not be compared with 

nuisance dust occupational exposure limits alone. Gravimetric results can be useful qualitatively 

to identify job functions or tasks where corrective action may be needed. 

REAL-TIME OR NEAR REAL-TIME TECHNIQUES FOR DIACETYL AND 

2,3-PENTANEDIONE

Several analytical methods can provide real-time or near real-time results of volatile compounds such as diacetyl and 2,3-pentanedione. These methods have the unique advantage to provide exposure information in real time to identify emission sources and tasks associated with 

exposure. Each of these on-site techniques requires specialized equipment and expertise in its use.

Fourier transform infrared spectroscopy can be used to analyze a sample of gaseous molecules for chemical composition and for the concentration of individual chemical constituents. 

In this analysis, chemical functional groups absorb infrared radiation at specific, unique frequencies producing a characteristic spectrum of absorbed versus transmitted radiation. From 

this spectrum, identification and quantification of the gas is possible.

Photoionization detectors (PID) can be used to monitor air contaminant concentrations 

in industrial work environments, including flavoring manufacturing facilities. Photoionization analysis has become a favored technique for on-site monitoring of volatile organic compounds because of ease of operation, reliability, versatility, cost, and response to a wide variety 

of substances. PIDs respond to a broad range of volatile compounds (including diacetyl and 

2,3-pentanedione) but do not provide concentrations specific to any particular compound. PIDs 

are often useful for process evaluation, identifying sources, and assessing control effectiveness.

Nondispersive infrared analysis also can be used to quantify many substances such as 

diacetyl or 2,3-pentanedione by determining the response relative to known concentrations of 

that substance at a selected analytical wavelength.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 5

CONTROLLING EXPOSURES

Controlling exposures to occupational hazards is the fundamental method of protecting 

workers. Traditionally, a hierarchy of controls has been used as a means of determining how 

to implement feasible and effective controls, which typically include: elimination, substitution, 

engineering controls, administrative controls and personal protective equipment (PPE). The 

idea behind the hierarchy of controls is that the methods at the top of the list are generally more 

effective in reducing the risk associated with a hazard than those at the bottom. Following the 

hierarchy normally leads to the implementation of inherently safer systems, ones where the risk 

of illness or injury has been substantially reduced.

To the extent possible, flavors should be compounded using the ingredients of lowest toxicity. For example, if a diacetyl substitute of lower toxicity that satisfies the requirements of the 

job is available, then this substitute should be used. Substitution of ingredients is often difficult, 

however, because of the many factors that determine suitability of a substitute as well as the 

dearth of knowledge on relative toxicity of potential substitutes. Diacetyl substitutes should not 

be assumed to be safe in the absence of toxicological data. The potential for workers’ exposure 

and disease from these substitutes still remains largely unstudied.

When applied and operating properly, engineering controls can reduce airborne contaminant 

concentrations, thereby mitigating worker exposures. NIOSH has identified control measures including engineering controls, administrative controls, and PPE to reduce worker exposure to hazardous 

substances during the production of powder and liquid flavorings [NIOSH 2004, 2008a,b,c; Dunn 

2007]. While much of this work emphasized the reduction of exposure to diacetyl, adoption of these 

control recommendations is anticipated to also reduce exposure to 2,3-pentanedione and other potentially harmful substances in the work environment. Many industries have implemented engineering controls to reduce exposure and risk of disease among their workers. Pharmaceutical companies 

have developed general design concepts and controls for common unit operations in manufacturing. 

These concepts provide a selection of approaches for working with hazardous materials including 

the specification of general ventilation; local exhaust ventilation (LEV); maintenance, cleaning, and 

disposal procedures; PPE; exposure monitoring, and; medical surveillance [Naumann et al. 1996].

The primary means for reducing exposures should be to implement process changes and engineering controls (e.g., LEV). Use of PPE should be the approach of last resort. Production processes 

differ among companies, so the approaches discussed below may not apply to all facilities. A sitespecific safety and health plan should be developed and should include guidance for recognizing hazardous exposures and strategies to control them. Special attention should be given to manual handling 

of flavoring ingredients, particularly in heated processes, and when spraying flavoring ingredients. 

The food and flavoring production industries have several primary processes that may result 

in the potential for worker exposure to diacetyl, 2,3-pentanedione, and other flavoring ingredients. 

These may be grouped, from an exposure standpoint, into a few general categories including production operations, packaging operations, cleaning, and maintenance operations [ERG 2008]. Table 1 

displays a list of job categories and major activities associated with these categories. For each major 

activity, the table indexes the figure(s) showing relevant engineering control systems. These processes include blending, mixing, and handling of flavoring ingredients in liquid and powder form. Bag 

emptying, bag filling, charging tanks, benchtop weighing and handling, and drum filling and emptying are a few of the production tasks of concern. The following sections discuss engineering controls 

that can be used to reduce workers’ exposures to diacetyl, 2,3-pentanedione, and other potential 

airborne hazards in the primary production processes used in the food and flavoring industries.
6 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

Table 1. Job categories and major activities of workers potentially exposed to flavorings in 

the food and flavor production industries, indicating relevant control information and local 

exhaust ventilation diagrams

Job category Major activities See figure

Production operator Benchtop weighing and handling 1, 2, 3

Charging/filling tanks, mixing 4, 5, 6, 7, 9

Bag emptying 10

Packaging personnel Drum filling and emptying 7, 8, 9

Bag filling 11, 12

ENGINEERING CONTROLS

Many of the recommended controls observed or developed in this industry involve some type 

of ventilation to remove the contaminant and introduce replacement air. Some broad considerations are presented below followed by descriptions of ventilation systems for specific operations. 

GENERAL VENTILATION

The use of supply and exhaust air throughout the facility can provide pressurization schemes 

that reduce the number of workers exposed to flavoring ingredients. Production areas should be 

kept at a negative pressure with respect to nearby areas. Exhaust air volume from the production 

area should be slightly greater than the volume of supply air. A general rule is to design the ventilation systems so that the supply flow rate is set at 5%–10% less than the exhaust flow rate; the difference should be at least 50 cubic feet per meter (cfm) [ACGIH 2013]. Air pressure differentials can 

be qualitatively checked between the production area and all neighboring areas by using an airflow 

visualization test. This simple test indicates whether air is flowing into or out of the production area 

[ACGIH 2007; Burgess et al. 2004]. Sources for airflow visualization tests (smoke tube/generator) 

are available from a number of commercial vendors.

VENTILATION CONSIDERATIONS

• Ensure that ventilation systems maintain the mixing or compounding rooms and other

areas where flavorings are handled under negative pressure relative to the rest of the

plant. This will reduce the spread of contaminants in the air of those rooms and areas to

the rest of the plant.

• Ensure that air from mixing or compounding rooms is not recirculated to other areas

of the facility and is exhausted directly to the outdoors. Contact the local air pollution

control agency to ensure compliance with emissions requirements for new or revised

engineering controls.

• Use a ventilated booth or partial enclosure to collect dusts and vapors during packaging

operations.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 7

• Position the collection hood as close as possible to the source of the flavoring ingredients

when using LEV.

• Install an indicator such as a manometer or pressure gauge fitted on the ducting near

the hood inlet to provide a way to check that the device is working properly. Check the

hood static pressure, face velocity and capture velocity on a periodic basis (monthly) and

record the results to ensure that the system is performing as designed.

• Install a control on/off light to indicate the status of the exhaust fan.

• Place the exhaust hood opening away from doors, windows, air supply registers, and

aisle ways to reduce the impact of cross drafts.

• Provide an air supply to the work area to replace most of the extracted air from LEV systems.

• Inspect hoods and enclosures for signs of damage or leaks (rust/corrosion, open access doors,

etc.) and obstructions (paper, gloves, rags, etc.). Where possible, use screens to prevent foreign objects from being pulled into the system through openings (slots, hood faces, etc.).

• Discharge vented air to unoccupied areas outdoors away from doors, windows, walkways, and air inlets to prevent re-entrainment. A properly designed exhaust stack can

help prevent re-entry of exhausted air into the building. Guidance on stack design is

available from a variety of organizations including: American Society of Heating, Refrigerating and Air-conditioning Engineers and the American Conference of Governmental

Industrial Hygienists [ACGIH 2013; ASHRAE 2011].

• Monitor workers’ exposures to assess effectiveness of the system after ventilation is installed.

GENERAL ENGINEERING CONSIDERATIONS

To the extent feasible, incorporate the following elements into the engineering design. 

• Use closed transfer processes to reduce worker exposure to emissions.

• Isolate the mixing area from the rest of the plant with walls, doors, or other barriers,

and keep this area under negative pressure with respect to the rest of the plant to reduce

dispersal of contaminants into adjacent work areas.

• Provide mechanical or pneumatic assistance with bag and sack handling.

• Place the work area away from doors, windows, and walkways to keep drafts from interfering with the ventilation and spreading contaminants.

SMALL-SCALE WEIGHING AND HANDLING OF FLAVORING INGREDIENTS

Small-scale weighing and handling of ingredients are common tasks used in flavoring production, bakeries, dairy production, and snack food manufacturing. The tasks of weighing out 

both dry and wet food ingredients can lead to worker exposure primarily through the scooping, 

pouring, and dumping of these materials. Because weighing and pouring are often performed 

on a benchtop workstation, the addition of slotted backdraft ventilation for both the bench and 

the weighing area is recommended (Figures 1 and 2). The use of engineering controls to reduce 

worker exposure to chemicals during mixing and weighing has been evaluated in flavoring 

production facilities [NIOSH 2008a,c]. In these facilities, compounders measured and poured 
8 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

flavoring ingredients on a bench and then transferred these mixtures to open tanks for liquid 

flavoring production or to blenders for powdered flavoring production.

Ventilated backdraft workstations used for small batch mixing have been evaluated in two 

field studies conducted in flavoring production plants (Figure 3) [NIOSH 2008a,c]. These stations were designed to maintain an air velocity of 100–150 feet per minute (fpm) at the face of 

the enclosure and reduced the exposures by 90%–97% when mixing tasks were performed using these stations. The selection of control velocity should be based on the material being used 

(powder versus liquid), plant conditions (background drafts), and momentum of contaminant 

source (pouring versus spraying or vigorous mixing).The use of baffles on the side and top of 

these workstations to better enclose the process provides improved performance and minimizes 

the deleterious effects of cross drafts on contaminant control. Plastic curtains can provide a 

reasonable enclosure and improve access to the bench area. Information on design criteria for 

these workstations is available from the American Conference of Governmental Industrial Hygienists and the U.K. Health and Safety Executive [ACGIH 2013; HSE 2003a].

FILLING, MIXING, AND EMPTYING LARGE MIXING TANKS

The addition of solid and liquid ingredients into tanks and other mixing vessels can cause 

exposure to dusts and vapors due to the displacement of air in the vessel. The use of LEV at 

the mixing tank helps to maintain the vessel at a negative pressure and contain evaporative 

emissions. Using a ventilated tank lid reduced the exposure of a worker when mixing a food 

flavoring by approximately 76% compared to the same operation without the ventilated tank 

lid (Figure 4) [NIOSH 2008c]. Ventilated tank lids have also been recommended by the U.K. 

Health and Safety Executive to contain vapors when mixing liquids with other liquids or solids 

[HSE 2003b]. Maintaining an air velocity of 100–150 fpm across the opening of the tank is recommended. A second design uses an annular exhaust slot hood to remove vapors from mixers 

(Figure 5) [HSE 2003c]. Another approach to controlling exposure when filling mixing vessels 

and tanks is to use a simple exhaust hood near the opening of fixed tanks (Figure 6); the inward 

velocity should be at least 200 fpm [HSE 2003d]. A NIOSH laboratory study of different mixing 

tank hood designs for a 4 foot diameter tank showed that capture efficiencies above 90% were 

possible for all hoods and configurations at an exhaust flow rate of 200 cfm with a crossdraft of 

100 fpm or less [Hirst et al. 2014].

The use of a ventilated mixing booth was evaluated to assess control of exposures from a 

large mixing tank (Figure 7). This booth allows a large portable mixing tank to be rolled inside 

so that chemical vapors emitted during pouring and mixing of flavoring ingredients in the tank 

are captured and exhausted outdoors. However, the booth can also be used for other production 

tasks such as large pouring and product packaging. The use of slots across the booth plenum 

helps to evenly distribute the flow across the height and width of the booth, and the use of side 

baffles/walls prevents room air drafts from reducing the effectiveness of the booth enclosure. 

A field study showed hood capture efficiencies of greater than 90% in tracer gas tests [NIOSH 

2008a]. An average air velocity of 100–150 fpm across the face of the booth is recommended. 

An important design consideration is to make the booth deep enough to completely contain the 

process. Activities performed outside of the face of the booth will be affected by room drafts and 

may not be effectively controlled. Workers should be trained to always ensure that the hood is 

operating properly and to place the flavoring between themselves and the exhaust slots.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 9

After mixing is finished, the flavoring is frequently transferred into drums or other containers for shipping. Care must be taken during fluid transfer whether using gravity flow or 

pump discharge. The use of ventilation at the tank or barrel opening has been recommended 

for capture of vapors during transfer of chemicals (Figures 8 and 9) [HSE 2003e; ACGIH 2013]. 

For flammable liquids, suitable fans and equipment as well as appropriate grounding schemes 

should be used to prevent the buildup and discharge of static electricity. In all cases, when 

transferring flammable liquids, grounding and bonding requirements should be met to prevent 

sparks and explosions [NFPA 2007].

DUMPING POWDERED INGREDIENTS INTO A BLENDER (BAG DUMPING)

Manual handling of solid powders is a process used in many industries, including food and 

flavoring production. Opening and dumping of bags of powdered ingredients is commonly 

performed by workers when producing flavorings, dairy products, snack foods, and in bakeries. Typically, a worker cuts open bags of material (e.g., 50-pound bags), dumps the ingredients 

into a hopper, and then stacks or disposes of the empty bags. In powdered flavoring production, 

these hoppers are commonly outfitted onto blenders used to load the base starch ingredient for 

dry flavor blends. Technology used to control dusts during bag dumping has been in place for 

many years.

The standard control for bag dumping consists of a hopper outfitted with an LEV system to 

pull dusts away from workers as they open and dump bags of powdered materials. A number of 

commercial vendors manufacture and sell bag dumping and handling stations. The designs for 

these devices are available from several sources of industrial ventilation guidance. One control 

approach specifies a face velocity of 200 fpm and includes a waste bag collection chute (Figure 

10) [HSE 2003f]. A secondary source of exposure is handling the bags following dumping. Reentrainment of dust contamination on the surface of the bag and handling/disposal of bags typically increases worker exposure. An integral pass through to a bag disposal chute/compactor 

might reduce dust exposure while bag handling. Other approaches, such as spraying the inside 

of bags with water before compacting, may also be beneficial in reducing dust re-entrainment 

[Heitbrink and McKinnery 1986].

DISCHARGING OF POWDERED FLAVORING FROM A BLENDER/SPRAY 

DRYER (BAG FILLING)

Powder flavorings are typically mixed in industrial blenders or produced by a spray drying 

process. For the blending process, a powdered starch or other carbohydrate is combined with 

a liquid or paste flavoring agent. When the blending or spray dry process is completed, the 

powder product may be discharged into a bulk tote or packaged into smaller containers. The 

use of a ventilated collar-type hood around the discharge point can reduce workers’ exposures 

to dust and vapors. The U.K. Health and Safety Executive has developed a control approach for 

filling bags with solid materials. The control specifies a ventilated enclosure around the powder 

discharge outlet and applies to filling smaller product bags as well as intermediate bulk containers (Figure 11) [HSE 2003g]. This design guidance recommends an air velocity of 200 fpm into 

the enclosure.
10 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

In addition to ventilation solutions, other dust control approaches have been used in a variety of industries and should be applicable for food and flavoring production. For example, 

an inflatable seal can be used to create a dust-tight seal on the discharge outlet of an industrial 

blender while the product is being unloaded. This method provides a simple technique to reduce dust escape during this process (Figure 12). Another system that could be used is the 

continuous liner system [Hirst et al. 2002]. In this system, the first liner is pulled down into the 

overpack (usually a 5-gallon bucket or a cardboard box). Product is discharged into the liner 

through a butterfly valve on the blender outlet. Once full, the top of the first liner sleeve is closed 

with tape or a fastener, or it is heat sealed and cut. The product is sealed within the poly-lined 

container, and a new sealed poly liner is pulled down to start discharge into the next container. 

This continuous process seals off the primary leak paths for dust when unloading an industrial 

blender or other equipment. These non-ventilation systems are commonly used in the pharmaceutical industry and may provide effective alternatives to the traditional LEV control systems.

ADMINISTRATIVE AND WORK PRACTICE CONTROLS

Engineering controls are the preferred methods for reducing occupational exposures. Administrative controls such as medical surveillance programs and work practice changes are the 

next steps. Safe work practices, incorporated into standard production procedures, can promote a safe and healthy workplace as well as improve efficiency and increase production. 

Following are recommended administrative and work practice controls:

• Establish, implement, and maintain a medical surveillance program for all exposed employees. Medical monitoring of exposed workers can identify early work-related health

effects in workers so that steps can be taken to prevent disease progression.

• Ensure workers do not eat, drink, or use tobacco products in the work area.

• Establish a hazard communication program that meets the requirements of the OSHA

hazard communication standard [29 CFR 1910.1200] and the Globally Harmonized

System of Classification and Labeling of Chemicals [OSHA 2006].

• Use a closed process wherever possible to transfer flavoring ingredients instead of manual

pouring. When poured, liquids should be added through a funnel into a covered mixing

vessel to limit spills. The work area should be kept clean and spills dealt with promptly.

• Develop procedures for assessing and maintaining ventilation systems, and document

them in a written plan. Periodic monitoring of system performance may include measurement of hood static pressure and face/duct velocity as well as smoke tube testing.

• Restrict access to all areas where flavorings are being handled openly to properly protect

workers (see section on PPE).

• Establish standard procedures for cleaning containers and mixing tanks. When possible,

use an initial cold water rinse followed by warm water cleaning to reduce volatilization.

• Establish standard procedures for cleaning up spills small and large, wet and dry.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 11

• Use a vacuum with a high efficiency particulate air filter or a wet cleaning technique. Do

not use compressed air and dry sweeping for cleaning, as these will re-entrain airborne

particulate into the environment.

• Cover containers used to mix and store flavoring ingredients when not in use. Keep

empty containers sealed as they may contain residual flavorings.

• Use cold storage for flavoring ingredients to reduce evaporation of chemicals into the

air. Volatile ingredients should be added while cold to mixtures. Do not use heat when

mixing flavoring ingredients.

• Wait until the pressure is at or below ambient to open pressurized vessels.

PERSONAL PROTECTIVE EQUIPMENT

Some forms of PPE (e.g., safety glasses, gloves) are designed to prevent skin contact and 

exposures other than inhalation. Respirators are designed to reduce inhalation exposure but 

should not be used as the primary means of controlling workers’ exposure to respiratory hazards for routine operations. Until risk can be assessed and compared with an occupational exposure limit, respirators should be used for exposure situations even when engineering controls 

are used. Workers may also need to use respirators during the implementation of engineering 

controls and work practices, during some short-duration maintenance and cleaning procedures, and during emergencies.

Following are recommendations regarding PPE:

• Instruct workers with potential exposure of the skin or eye to flavoring ingredients to

use chemical resistant gloves and eye protection.

• Require all exposed workers to wash hands and face before eating, drinking, or smoking

even in situations where gloves, face shields, and other PPE are used.

• Monitor each process to accurately determine the 8-hour time-weighted average and the

short-term exposure levels of airborne diacetyl and 2,3-pentanedione to which employees may be exposed. Provide respiratory protection when potential exposures to diacetyl

or 2,3-pentanedione exist.

• Establish a respiratory protection program that meets the requirements of the OSHA respiratory protection standard when respiratory protection is used [29 CFR 1910.134]. The

provisions of this program include determination of tasks which require respirator use, procedures for selection, medical evaluation, fit testing, training, use, and care of respirators.

— Consider using powered air purifying respirators or supplied air respirators 

with a full facepiece, hood, helmet, or loose-fitting facepiece for respiratory 

protection against diacetyl and 2,3-pentanedione, particularly if workers are 

expected to wear a respirator for an extended period of time.

— Use, at a minimum, a NIOSH-certified air-purifying full facepiece respirator 

with organic vapor and P100 cartridge(s) or canister(s). 

Additional information on the selection and use of respirators can be found in the NIOSH Respirator Selection Logic [NIOSH 2004].
12 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

ADDITIONAL INFORMATION

New information is continuing to evolve in regard to diacetyl and 2,3-pentanedione. Practitioners are encouraged to stay abreast of new findings through several timely websites and products including the following:

• http://www.cdc.gov/niosh/topics/flavorings

• http://www.cdc.gov/niosh/docket/archive/docket245.html

• http://www.osha.gov/SLTC/flavoringlung/index.html

• http://www.ansi.org (Z9 Standard)

• http://www.hse.gov.uk/coshh/essentials (Engineering Control Guidance)

• http://www.acgih.org (Ventilation Manual)

REFERENCES

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Akpinar-Elci M, Travis WD, Lynch DA, Kreiss K [2004]. Bronchiolitis obliterans syndrome in 

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production plant. J Occup Environ Hyg 9:D33–34.

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the flavor-manufacturing industry—California, 2004–2007. MMWR 56(16):389–393. 

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Environ Hyg 8(2):93–103. 

Department of Commerce [2004]. 2002 Economic Census Manufacturing Industry Series: 

Spice and extract manufacturing: 2002; Flavoring syrup and concentrate manufacturing: 

2002. Washington, DC: U.S. Department of Commerce. [http://www.census.gov/prod/ec02/

ec0231i311942t.pdf]. Date accessed: March 2008. 

Dunn KH [2007]. Letter of March 23, 2007, from KH Dunn, Division of Applied Research and 

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ERG [2008]. Technological and economic feasibility analysis for proposed OSHA standard for 

diacetyl and acetoin. Draft final report. Lexington, MA. By: Eastern Research Group Inc.

EPA (Environmental Protection Agency) [2002]. Non-confidential inventory updating report. 

[http://www.epa.gov/iur/tools/data/2002-vol.html]. Date accessed: March 2011. 

Hallagan [2010]. Personal communication from John Hallagan, General Counsel Flavor Extract 

Manufacturers Association, based upon 2010 Industry Survey, received October 19, 2010.

Heitbrink WA, McKinnery Jr. WN [1986]. Dust control during bag opening, emptying and 

disposal. Appl Ind Hyg 1(2):101–109. 

Hirst DVL, Dunn KH, Shulman SA, Hammond DR, Sestito N [2014]. Evaluation of engineering controls for the mixing of flavorings containing diacetyl and other volatile ingredients. 

J Occup Environ Hyg 11(10): 680–687.

Hirst N, Ryder M, Brocklebank M [2002]. Containment systems: a design guide. Rugby, Warwickshire, U.K.: Gulf Professional Publishing. 

HSE [2003a]. Weighing and handling flour improvers etc. (craft bakery). Flour control guidance 

sheet FL02. In: COSHH Essentials: Easy steps to control chemicals: Control of Substances 

Hazardous to Health Regulations. London: U.K. Health and Safety Executive.

HSE [2003b]. Mixing liquids with other liquids or solids. Control guidance sheet 217. In: 

COSHH Essentials: Easy steps to control chemicals: Control of Substances Hazardous to 

Health Regulations. London: U.K. Health and Safety Executive.

HSE [2003c]. Mixing solids with other solids or liquids. Control guidance sheet 215. In: COSHH 

Essentials: Easy steps to control chemicals: Control of Substances Hazardous to Health Regulations. London: U.K. Health and Safety Executive.

HSE [2003d]. Charging reactors and mixers from a sack or keg. Control guidance sheet 210. 

In: COSHH Essentials: Easy steps to control chemicals: Control of Substances Hazardous to 

Health Regulations. London: U.K. Health and Safety Executive.

HSE [2003e]. Drum filling. Control guidance sheet 212. In: COSHH Essentials: Easy steps to 

control chemicals: Control of Substances Hazardous to Health Regulations. London: U.K. 

Health and Safety Executive.

HSE [2003f]. Sack emptying. Control guidance sheet 208. In: COSHH Essentials: Easy steps to 

control chemicals: Control of Substances Hazardous to Health Regulations. London: U.K. 

Health and Safety Executive.

HSE [2003g]. Sack filling. Control guidance sheet 206. In: COSHH Essentials: Easy steps to 

control chemicals: Control of Substances Hazardous to Health Regulations. London: U.K. 

Health and Safety Executive.

Hubbs AF, Cumpston AM, Goldsmith WT, Battelli LA, Kashon ML, Jackson MC, Frazer DG, 

Fedan JS, Goravanahally MP, Castranova V, Kreiss K, Willard PA, Friend S, SchweglerBerry D, Fluharty KL, Sriram K [2012]. Respiratory and olfactory cytotoxicity of inhaled 

2,3pentanedione in Sprague-Dawley rats. Am J Pathol 181(3):829–844.

Hubbs AF, Moseley AE, Goldsmith WT, Jackson MC, Kashon ML, Battelli LA, Schwegler-Berry 

D, Goravanahally MP, Frazer D, Fedan JS, Kreiss K, Castranova V [2010]. Airway epithelial 

toxicity of the flavoring agent, 2,3-pentanedione. The Toxicologist CD—An official Journal 

of the Society of Toxicology 114(S-1):319. 

Kanwal R, Kullman G, Piacitelli C, Boylstein R, Sahakian N, Martin S, Fedan K, Kreiss K [2006]. 

Evaluation of flavorings-related lung disease risk at six microwave popcorn plants. J Occup 

Environ Med 48(2):149–157. 
14 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

Kreiss K, Gomaa A, Kullman G, Fedan K, Simoes EJ, Enright PL [2002]. Clinical bronchiolitis 

obliterans in workers at a microwave-popcorn plant. N Engl J Med 347(5):330–338. 

Lockey JE, Hilbert TJ, Levin LP, Ryan PH, White KL, Borton EK, Rice CH, McKay RT, LeMasters GK [2009]. Airway obstruction related to diacetyl exposure at microwave popcorn 

production facilities. Eur Respir J 34(1):63-71. 

Martyny JW, Van Dyke MV, Arbuckle S, Towle M, Rose CS [2008]. Diacetyl exposures in the 

flavor manufacturing industry. J Occup Environ Hyg 5(11):679–688.

Morgan DL, Jokinen MP, Johnson CL, Gwinn WM, Price HC, Flake GP [2012a]. Bronchial 

fibrosis in rats exposed to 2,3-butanedione and 2,3-pentanedione vapors. Toxicol Sci (The 

Toxicologist) 126:186.

Morgan DL, Jokinen MP, Price HC, Gwinn WM, Palmer SM, Flake GP [2012b]. Bronchial and 

bronchiolar fibrosis in rats exposed to 2,3-pentanedione vapors: implications for bronchiolitis obliterans in humans. Toxicol Pathol 40(3):448–465. Epub 2012 Jan 3.

Morgan DL, Kirby PJ, Price HC, Bosquet RW, Taylor GJ, Gage N, Flake GP [2010]. Inhalation 

toxicity of acetyl proprionyl in rats and mice. Abstract 1492, The Toxicologist CD—An official Journal of the Society of Toxicology, Volume 114, Number S-1, March 2010.

Naumann BD, Sargent EV, Starkman BS, Fraser WJ, Becker GT, Kirk GD [1996]. Performancebased exposure control limits for pharmaceutical active ingredients. AIHA J 57(1):33–42. 

NFPA [2007]. NFPA 77: Recommended Practice on Static Electricity. Quincy, MA: National 

Fire Protection Association. 

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U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication 

No. 2004-110. 

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flavoring chemicals at Gold Coast Ingredients, Inc. Commerce, CA. Cincinnati, OH: U.S. 

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National Institute for Occupational Safety and Health. Survey Report No. EPHB 322–11a. 

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exposures and work practices at Gold Coast Ingredients, Inc. Technical Assistance Report 

to CAL-OSHA. Cincinnati, OH: U.S. Department of Health and Human Services, Centers 

for Disease Control and Prevention, National Institute for Occupational Safety and Health, 

NIOSH HETA Report No. 2006-0361-1. 

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of liquid and powder flavoring chemicals at Kerry Ingredients and Flavours, Inc. formerly 

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0155-3131.

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and 2,3-pentanedione. U.S. Department of Health and Human Services, Centers for Disease 
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Control and Prevention, National Institute for Occupational Safety and Health. DHHS 

(NIOSH) Publication No. 2011-XXX. [http://www.cdc.gov/niosh/docket/archive/pdfs/

NIOSH-245/0245-081211-draftdocument.pdf].

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PF, eds. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS 

(NIOSH) Publication 94-113 (August 1994); 1st Supplement Publication 96-135, 2nd Supplement Publication 98-119; 3rd Supplement 2003-154. 

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Chemicals (GHS). Washington, DC: U.S. Department of Labor, Occupational Safety and 

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OSHA [2008a]. OSHA technical manual. Section II: Sampling, measurement methods and instruments. Washington, DC: U.S. Department of Labor, Occupational Safety and Health 

Administration. [http://www.osha.gov/dts/osta/otm/otm_ii/otm_ii_1.html]. Date accessed: 

June 2013.

OSHA [2008b]. OSHA sampling and analytical methods. Hendricks W, ed. Salt Lake City, 

UT: U.S. Department of Labor, Occupational Safety and Health Administration. Acetoin/

Diacetyl 1013. [http://www.osha.gov/dts/sltc/methods/validated/1013/1013.html]. Date accessed: June 2009. 

OSHA [2008c]. OSHA sampling and analytical methods. Hendricks W, ed. Salt Lake City, 

UT: U.S. Department of Labor, Occupational Safety and Health Administration. Acetoin/

Diacetyl 1012. [http://www.osha.gov/dts/sltc/methods/validated/1012/1012.html]. Date accessed: June 2009.

OSHA [2010]. OSHA sampling and analytical methods. Hendricks W, ed. Salt Lake City, UT: 

U.S. Department of Labor, Occupational Safety and Health Administration. 2,3-Pentanedione 1016. [http://www.osha.gov/dts/sltc/methods/validated/1016/1016.pdf]. Date accessed: 

March 2011.
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Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 17

FIGURE 1*

Benchtop ventilation for weighing/handling powders

W

Baffles are

desirable

Maximum plenum velocity

1/2 slot velocity

12”

24”

Slots-size for 2000 feet

per minute

45o

 taper angle

100 feet per 

minute

*VS–90–01, From ACGIH, Industrial Ventilation: A Manual of Recommended Practice for Design, 27th Edition.

Copyright 2010. Reprinted with permission.
18 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

FIGURE 2*

Benchtop ventilation for weighing/handling powders

0.5 to 1 

meters per 

second

100 to 200 feet 

per minute

*Contains public sector information published by the Health and Safety Executive and licensed under the Open

Government License v1.0.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 19

FIGURE 3

Ventilated small batch mixing workstation

100–150 feet per minute

into booth
20 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

FIGURE 4

Mixing vessel with a ventilated hinged tank lid

100–150 feet per minute
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 21

FIGURE 5*

Annular exhaust for capturing vapors from mixers

Exhaust

Airflow across 

whole mixer top 

toward the LEV 

should be at 

least 1 meters 

per second (200 

feet per minute).

*Contains public sector information published by the Health and Safety Executive and licensed under the Open

Government License v1.0.
22 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

FIGURE 6*

Charging reactors and mixers from a sack or keg

Exhaust

Exhaust

Minimum airflow

1 meters per second

Charging port

200 feet per minute

*Contains public sector information published by the Health and Safety Executive and licensed under the Open

Government License v1.0.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 23

FIGURE 7

Ventilated booth for large batch mixing
24 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

FIGURE 8*

Annular exhaust for capturing vapors during drum filling

SIDE VIEW

OVERHEAD VIEW

Exhaust

Feed pipe

Airflow across drum cap should be at least 0.5 meters per 

second (100 feet per minute) capture.

*Contains public sector information published by the Health and Safety Executive and licensed under the Open

Government License v1.0.
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 25

FIGURE 9*

Ventilation design options for capturing vapors during drum filling

Q = 100 cfm/ft2 barrel top (minimum)

Minimum duct velocity = 3500 fpm

he = 1.78 VPs + 0.25 VPd

Q = 150 cfm/ft2 of open face area

Minimum duct velocity = 3500 fpm

he = 0.25 VPd (45o

 taper)

Q = 300–400 cfm

Minimum duct velocity = 3500 fpm

he = 0.25 VPd

Q = 50 cfm × drum diam. (ft)

Minimum duct velocity = 3500 fpm

he = 0.25 VPd

Flex duct

Exhaust duct

Puer Hood Feed spout

3” min. dia.

Q

1” max.

45o

D + 12”

Close clearance

D

45o

Note 1: Air displaced by material feed rate may require higher exhaust ow rates.

Note 2: Excessive airow can cause loss of product.

Note 3: When transferring ammable or combustible liquids, bonding

 and grounding requirements of NFPA Code 77 should be followed.

*VS-15-01, From ACGIH, Industrial Ventilation: A Manual of Recommended Practice for Design, 27th Edition. Copyright

2010. Reprinted with permission.
26 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

FIGURE 10*

Ventilated bag dumping/emptying station

Exhaust

1.0 meters per 

second minimum 

airflow

Waste bag collection Open grill work shelf

*Contains public sector information published by the Health and Safety Executive and licensed under the Open

Government License v1.0.

200 feet per 

minute
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 27

FIGURE 11*

 Ventilation for bag filling

Feed hopper

Exhaust

Partial

enclosure

around lling

head

Bag clamp

Grid area to

catch spillages

Provide a ventilated 

enclosure around filling point 

with an inward airflow of at 

least 1 meters per second 

(200 feet per minute).

*Contains public sector information published by the Health and Safety Executive and licensed under the Open

Government License v1.0.
28 Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

FIGURE 12

Dust control during bag filling operation
Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione 29

This document is in the public domain and may be freely copied or reprinted. 

NIOSH encourages all readers of the Best Practices documents to make them available 

to all interested employers and workers.

As part of the Centers for Disease Control and Prevention, NIOSH is the federal 

agency responsible for conducting research and making recommendations to prevent 

work-related illness and injuries. Best Practices documents are based on research studies that show how worker exposures to hazardous agents or activities can be significantly reduced. 
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DHHS (NIOSH) Publication No. 2015-197

safer • healthier • peopleTM