Health Hazard Evaluation Report 2017-0059-3291 Page 1 

 

Evaluation of 3-D Printer Emissions and
 

Personal Exposures at a Manufacturing
 

Workplace 

Report No. 2017-0059-3291 

August 2017 

Aleksandr B. Stefaniak, PhD, CIH 

Duane R. Hammond, MS, PE 

Alyson R. Johnson, MPH 

Alycia K. Knepp, BSc 

Ryan F. LeBouf, PhD, CIH 

U.S. Department of Health and Human Services 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health 
Page 2 

Contents 

Highlights...............................................i 

Abbreviations ..................................... iv 

Summary .............................................. 1 

Introduction......................................... 2 

Background.......................................... 2 

Process Description ............................. 2 

Methods ............................................... 3 

Results .................................................. 8 

Discussion .......................................... 33 

Conclusions ........................................ 35 

Recommendations............................. 36 

References.......................................... 38 

Acknowledgements........................... 42 

The employer is required to post a copy of this report for 30 days at or near the 

workplace(s) of affected employees. The employer must take steps to ensure 

that the posted report is not altered, defaced, or covered by other material. 

The cover photo is a close-up image of sorbent tubes, which are used by the HHE 

Program to measure airborne exposures. This photo is an artistic representation that may 

not be related to this Health Hazard Evaluation. 

Health Hazard Evaluation Report 2017-0059-3291 
Health Hazard Evaluation Report 2017-0059-3291 Page i 

Highlights of this Evaluation 

The Health Hazard Evaluation Program received a management request from a facility 

that manufactures products using 3-dimensional printing. The owner was concerned about 

employee exposures to emissions from the 3-dimensional printers. 

What We Did 

● We visited the manufacturing facility in April 2017. 

●	 We evaluated 3-dimensional printer emissions and measured personal exposures to 

printer workers. 

● We evaluated different ways to reduce 

emissions from the 3-dimensional printers. 

What We Found 

●	 Particles and organic chemicals were emitted 

from the 3-dimensional printers when using 

poly lactic acid and acrylonitrile butadiene 

styrene filaments. 

●	 Concentrations of particles and organic 

chemicals released by the 3-dimensional 

printers were similar when using poly lactic 

acid and acrylonitrile butadiene styrene 

filaments. 

● Particles and organic chemicals emitted from 

the 3-dimensional printers do not infiltrate into 

the Engineer’s Office.
	

● Loose-fitting doors and covers provided by the printer manufacturer did not prevent 

We evaluated concerns that 

employees were exposed 

to particles and vapors at 

a manufacturing facility 

that utilizes 3-dimensional 

printing. We found that 

personal exposures were well 

below established regulatory 

limits for specific chemicals, 

though if changes are made 

to the existing process, the 

employer should reassess 

personal exposures and 

emissions. 

particles and organic vapors from being released into air in the Print Room. 

● A custom-built ventilated enclosure effectively reduced particle concentration in the 

Print Room by over 99% and reduced the total organic chemical concentration by 

almost 70%. 

●	 Particles and organic chemicals were released into air during warm-up and use of the 

injection molding machine in the High Bay. 

●	 Personal exposures occurred to organic chemicals though levels were all well below 

established regulatory limits. 

What the Employer Can Do 

●	 If changes are made to the existing process, the employer should reassess personal 

exposures and emissions. 
Page ii Health Hazard Evaluation Report 2017-0059-3291

What Employees Can Do 

● Close the door to the Engineer’s Office when performing injection molding, grinding, 

or other tasks in the High Bay that generate particles and organic vapors. 

● Be aware of how specific tasks influence exposures and that changes in how work is 

performed could increase exposure. 
Health Hazard Evaluation Report 2017-0059-3291 Page iii 

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Page iv Health Hazard Evaluation Report 2017-0059-3291

Abbreviations
 

μm Micrometer 

ABS Acrylonitrile butadiene styrene 

ACGIH American Conference of Governmental Industrial Hygienists 

cm3 cubic centimeter of air 

CNC Condensation nuclei counter 

DC Diffusion charger 

NIOSH National Institute for Occupational Safety and Health 

nm Nanometer 

OEL Occupational exposure limit 

OPC Optical particle counter 

OSHA Occupational Safety and Health Administration 

PEL Permissible exposure limit 

PLA Poly lactic acid 

ppb Parts per billion 

ppm Parts per million 

REL Recommended exposure limit 

STEL Short-term exposure limit 

TLV Threshold limit value 

TWA Time-weighted average 

TVOC Total volatile organic chemicals 

μg/m3 Micrograms per cubic meter of air 

VOC Volatile organic chemicals 
Health Hazard Evaluation Report 2017-0059-3291 Page 1 

 

Summary 

We evaluated volatile organic compound and particle emissions from fused deposition 

modelingTM 3-D printers using poly lactic acid and acrylonitrile butadiene styrene 

thermoplastics and measured personal exposures to total and specific volatile organic 

compounds. The 3-dimensional printers emitted both volatile organic compounds and small 

particles during operation. Levels of all individual volatile organic compounds that were 

quantified on personal samples were well below applicable occupational exposure limits and 

guidelines. None of the employees reported any respiratory symptoms. At this time, we do 

not recommend any controls to lower exposures as they are already well-below established 

regulatory limits. Similarly, at this time we do not recommend the need to lower total particle 

number and total volatile organic chemical concentrations as there is no available guidance 

on appropriate levels. It is important to note that 3-D printing has not been thoroughly 

evaluated to determine its safety. As such, new information may become available in the 

future which may change our current perspective on the necessity of controls. 
Page 2 Health Hazard Evaluation Report 2017-0059-3291

Introduction 

The Health Hazard Evaluation Program of the National Institute for Occupational Safety 

and Health (NIOSH) received a request from a facility that manufactures products using 

3-dimensional (3-D) printing. The owner was concerned about employee exposures to 

particles and vapors that are emitted from fused deposition modelingTM 3-D printers using 

poly lactic acid (PLA) and acrylonitrile butadiene styrene (ABS) thermoplastics as well 

as injection molding with ABS thermoplastic. We visited the facility in April 2017 and 

measured levels of particles and organic chemicals in air and evaluated two different ways to 

reduce emissions from the 3-dimensional printers – use of the covers and doors provided by 

the printer manufacturer and use of a ventilated enclosure custom built by NIOSH. 

Background 

Additive manufacturing is a family of technologies used to build objects (usually layerby-layer) from a computer-assisted design computer file. At this facility, a specific type of 

additive manufacturing technology called fused deposition modelingTM, more commonly 

known as 3-D printing, is used to make objects. In this technique, a polymer filament is 

heated and extruded through a nozzle onto a build plate to create an object. During heating, 

the polymer filament degrades and releases ultrafine particles (size less than 100 nanometers 

[nm]) and organic chemicals into the air. There is growing interest in understanding the 

characteristics of these emissions. In particular, when breathed in, ultrafine particles are small 

enough to reach the deepest part of the lung where they can deposit. Once deposited in the 

lung, it is difficult for the body to efficiently remove these small particles. Breathing in small 

particles and some organic chemical vapors is associated with irritating the lungs or asthma 

[Yi et al. 2016; Stefaniak et al. 2017]. 

Process Description 

The company operates in leased space that occupies one half of a single-level building. 

We estimate that the company operates in about 24,000 square feet and consists of a Print 

Room which houses the 3-D printers, a High Bay where post-processing tasks and injection 

molding are performed, and an Engineer’s Office where computer work is performed. At this 

facility, 3-D printing is used to make cup holders with add-ons such as handles and clips and 

various other objects. PLA filament is primarily used at this facility, though ABS was also 

printed during our site visit as the company is considering its use in the future. 

At the time of our visit, the company had two full-time employees, an Engineer and the 

owner, and several part-time interns that also worked in the facility. Employees worked 

varying hours throughout the day from Monday through Friday. The Print Room had a 

rectangular floor plan with a drop ceiling and linoleum flooring (volume of 1570 cubic feet). 

There were 10 “desktop-scale” 3-D printers arranged on shelves 2 high by 5 wide and one 

freestanding industrial-scale 3-D printer (not in use at the time of our survey). A recirculating 

wall-mounted air conditioning unit was in the print room but no ventilation. The High Bay 

had a rectangular floor plan with concrete flooring (volume of 20,000 cubic feet) and was 

isolated from the Print Room and Engineer’s Office by a wall. The door between the High 
Health Hazard Evaluation Report 2017-0059-3291 Page 3 

Bay and the Print Room remained closed; whereas, the door to the Engineer’s Office was 

(usually) open. The High Bay contained several work benches which serve various purposes 

such as shipping area, post-processing of printed products, injection molding, and general 

machining. Post-processing tasks included sanding objects and “light” torching to brighten 

object colors. At the time of our survey, the company was exploring the feasibility of using 

a custom-built injection molding machine with ABS plastic to produce products. In the High 

Bay, there was only general ventilation for occupant comfort. The Engineer’s Office was of 

the same construction as the Print Room but slightly smaller (volume of 1260 cubic feet) and 

contained two desks and a computer. The Engineer’s Office and Print Room were separated 

by a wall that went from the floor to the drop ceiling but not to the building roof. 

The full-time employees and interns designed objects on a computer in the Engineer’s 

Office and communicated the build files to the 3-D printers. They entered the Print Room 

throughout the day for short periods of time to check on the status of prints, remove built 

products, or trouble shoot and fix problems if they arose. In the High Bay, employees 

manually sanded printed objects using an aluminum grit sandpaper and light torched printed 

objects using a butane torch to draw pigment colors out of the filament and brighten product 

color after sanding. Additionally, the owner operated the injection molding machine on an asneeded basis. Once finished, products were packaged for shipment. 

Methods 

Our primary objectives were to evaluate: 

1. chemical and particle emissions from the desktop-scale 3-D printers under normal 

work conditions with PLA filament; 

2.	 whether emissions changed if printing with ABS filament; 

3.	 if emissions from the Print Room infiltrated into the Engineer’s Office; 

4.	 whether the manufacturer-provided covers and doors of the 3-D printers were effective 

in reducing emissions; 

5.	 whether a ventilated enclosure system with filtration was effective in reducing 

emissions;
 

6.	 the influence of post-processing tasks and injection molding on emissions; and, 

7. employees’ exposures to volatile organic chemicals (VOCs). 

To achieve these objectives, we performed air sampling for airborne particles and/or organic 

vapors during 3-D printing and during specific tasks (e.g., sanding, torching, injection 

molding) and observed work practices over three days. 

Air sampling for particles in general workplace air 

We evaluated airborne particles in each work area using two types of techniques, the first is 

referred to as “real-time” monitoring and the second is called “time-integrated” sampling. 

For real-time monitoring, we used instruments that measure the particles very rapidly (one 

second to one minute intervals) and visually display the results on the instrument. The 
Page 4 Health Hazard Evaluation Report 2017-0059-3291

measurement data is also stored on an internal memory for analysis at a later time. Real-time 

instruments have the advantage of performing measurements quickly, which allowed us to 

identify specific emission sources (3-D printers) and see how changes in processes or tasks 

influenced the characteristics of particles in the air. A disadvantage of real-time instruments is 

that they measure all particles and cannot tell us if they were emitted from a specific source 

such as the 3-D printers. In time-integrated sampling, air is drawn through a filter for a 

period of time to collect particles. The filter is later analyzed in a laboratory to determine the 

properties of the collected particles. A major advantage of time-integrated sampling is that we 

can visualize the particles on the filter, which can be helpful to determine if airborne particles 

have size and shape consistent with emissions from the 3-D printers. 

Table 1 summarizes the real-time instruments used to monitor airborne particles in each work 

area. We measured particle number concentration using a condensation nuclei counter (CNC) 

(Model 8525, TSI Inc., Shoreview, MN), particle size distribution using an optical particle 

counter (OPC) (Model 1.108, GRIMM Aerosol Technik GmbH & Co. Ainring, Germany) 

or a mobility analyzer (Nanoscan) (Model 3910, TSI Inc., Shoreview, USA), and particle 

surface area using a diffusion charger (DC) (Model DC 2200 CE, EcoChem Analytics, 

League City, TX). 

Table 1. Real-time air monitoring instruments for particles 

Instrument What it measures 

Optical particle counter (OPC) Number and size of particles from 300 nm to >20 μm 

Condensation nuclei counter (CNC) Number of particles from 20 to 1000 nm 

Mobility analyzer (NanoScan) Number and size of particles from 10 to 420 nm 

Diffusion charger (DC) Surface area of particles 

We performed time-integrated sampling for airborne particles using 37-millimeter diameter 

track-etched polycarbonate filters with 0.8 μm pore size (SKC Inc., Eighty Four, PA) 

mounted in close-faced 37 millimeter plastic cassettes by drawing air through the membrane 

at 2 liters per minute using calibrated sampling pumps. We analyzed the filters at NIOSH 

using a field emission-scanning electron microscope to evaluate size and shape of particles. 

This microscopy is able to visualize particles with sizes less than 100 nm. We also used a 

technique called energy dispersive x-ray analysis to determine the chemical elements in 

collected particles. 

Air sampling for organic chemicals in general workplace air 

We evaluated organic chemicals in air using real-time monitoring instruments and timeintegrated sampling. We used a real-time monitor to rapidly measure the concentrations of 

organic chemicals in air, but it could not identify which specific chemicals were present. 

As such, a time-integrated sampler was used to collect air in a canister. The canister was 

transported back to NIOSH for analysis in our laboratory to identify specific chemicals and 

their concentrations. 

We measured real-time total volatile organic chemical (TVOC) concentrations using a 
Health Hazard Evaluation Report 2017-0059-3291 Page 5 

photoionization detector (RAE Systems, San Jose, USA or Ion Science Inc., Stafford, TX) 

to monitor fluctuations in organic chemical levels during specific activities and work tasks. 

The TVOC monitors were factory calibrated using isobutylene gas and span checked with 

isobutylene gas prior to use. We collected air samples using 450 milliliter Silonite® coated 

evacuated canister (Entech Instruments, Simi Valley, CA) samplers over a period of 6 

hours (in work areas) or over 30 seconds (during specific tasks) to quantify specific VOCs. 

We analyzed air collected in the canister samplers at NIOSH using a pre-concentrator/gas 

chromatograph/mass spectrometer system pursuant to a published method validation study 

[LeBouf et al. 2012] but modified to use a Model 7200 (Entech Instruments, Inc., Simi 

Valley, CA) pre-concentrator. All quantitative measurement results were corrected for the 

concentration of VOCs measured on background samples collected in workplaces. 

Environmental conditions in general workplace air 

We monitored general environmental conditions in each work area using two real-time 

instruments. We used a gas sensitive semiconductor sensor (Model S500, Ozone Solutions, 

Hull, IA) to monitor ozone concentrations and an environmental monitor (Velocicalc, Model 

9565, TSI Inc.) to monitor temperature and carbon dioxide and carbon monoxide levels. 

Sampling locations 

We monitored air and collected samples in the Print Room, Engineer’s Office, and the High 

Bay. For each work area on each day, we placed the real-time monitors and time-integrated 

samplers in a basket attached to a tripod (Figure 1) and positioned at the approximate height 

of a worker’s head. The tripod in the Engineer’s Office was designated Location 1. We placed 

two tripods in the Print Room; the first was next to the 3-D printers and designated Location 

2, and the other was just inside the doorway to the room and referred to as Location 3. We 

used individual instruments and samplers to evaluate tasks at different locations in the High 

Bay. 
Page 6 Health Hazard Evaluation Report 2017-0059-3291

Figure 1. Area sampling station showing real-time monitors and time-integrated samplers in 

the Print Room. Photo by NIOSH. 

Personal exposure monitoring 

We collected two samples each day to evaluate the Engineers’ personal exposures to VOC 

vapors. Samples were collected from the workers’ breathing zone (near the head). We 

evaluated TVOC levels using a real-time photoionization detector (Cub personal VOC 

detector, Ion Science Inc.) and observed work activities to understand the contribution of 

work to exposures. Additionally, we collected 450 milliliter evacuated canister samplers over 

a period of 6 hours for laboratory analysis to identify specific VOCs as described previously. 

Additionally, at the end of the work shift, we administered a questionnaire asking employees 

if they experienced any respiratory symptoms and other symptoms at work. 

NIOSH investigators refer to mandatory (legally enforceable) and recommended 

occupational exposure limits (OELs) for chemical, physical, and biological agents when 

evaluating workplace hazards. OELs have been developed by federal agencies and safety and 

health organizations to prevent adverse health effects from workplace exposures. Generally, 

OELs suggest levels of exposure that most employees may be exposed to for up to 8-10 
Health Hazard Evaluation Report 2017-0059-3291 Page 7 

hours per day, 40 hours per week, for a working lifetime, without experiencing adverse health 

effects. However, not all employees will be protected if their exposures are maintained below 

these levels. Some may have adverse health effects because of individual susceptibility, a 

pre-existing medical condition, or a hypersensitivity (allergy). In addition, some hazardous 

substances act in combination with other exposures, with the general environment, or with 

medications or personal habits of the employee to produce adverse health effects. Most OELs 

address airborne exposures, but some substances can be absorbed directly through the skin 

and mucous membranes. 

Most OELs are expressed as a TWA exposure. A TWA refers to the average exposure during 

a normal 8- to 10-hour workday. Some chemical substances and physical agents have 

recommended short-term exposure level (STEL) or “ceiling” values. Unless otherwise noted, 

the STEL is a 15-minute TWA exposure. It should not be exceeded at any time during a 

workday. The ceiling limit should not be exceeded at any time. 

In the United States, OELs have been established by the Occupational Safety and Health 

Administration (OSHA). The U.S. Department of Labor OSHA permissible exposure limits 

(PELs) (29 CFR 1910 [general industry]; 29 CFR 1926 [construction industry]; and 29 

CFR 1917 [maritime industry]) are legal limits. These limits are enforceable in workplaces 

covered under the Occupational Safety and Health Act of 1970. OSHA PELs represent the 

legal maximum for a TWA exposure to a physical or chemical agent over a work shift [OSHA 

2016]. OSHA STELs are the legal maximum average exposure for a 15-minute time period. 

Some chemicals also have an OSHA ceiling value which represent levels that must not be 

exceeded at any time. 

NIOSH recommended exposure limits (RELs) are recommendations based on a critical 

review of the scientific and technical information and the adequacy of methods to identify 

and control the hazard. NIOSH RELs are published in the NIOSH Pocket Guide to Chemical 

Hazards [NIOSH 2010]. NIOSH also recommends risk management practices (e.g., 

engineering controls, safe work practices, employee education/training, personal protective 

equipment, and exposure and medical monitoring) to minimize the risk of exposure and 

adverse health effects. NIOSH provides REL values as TWA concentrations that should 

not be exceeded over an 8- or 10-hour work shift, during a 40-hour workweek [NIOSH 

2010]. NIOSH also provides STELs which are 15-minute TWA exposures that should not be 

exceeded [NIOSH 2010]. 

Other OELs commonly used and cited in the United States include threshold limit 

values (TLVs®) which are recommended by the American Conference of Governmental 

Industrial Hygienists (ACGIH). ACGIH is a professional, not-for-profit scientific 

association that reviews existing published, peer-reviewed scientific literature and publishes 

recommendations for levels of substances in air based on an 8-hour workday and 40-hour 

workweek. These recommendations are called TLVs [ACGIH 2016]. ACGIH TLVs are 

not standards; they are health-based guidelines derived from scientific and toxicological 

information. ACGIH provides TLV-TWA guidelines that are levels that should not be 

exceeded during any 8-hour workday of a 40-hour workweek. ACGIH also provides TLV­
Page 8 Health Hazard Evaluation Report 2017-0059-3291

STEL guidelines which are 15-minute exposure levels that should not be exceeded during a 

workday. Exposures above the TLV-TWA but less than the TLV-STEL should be (1) less than 

15 minutes, (2) occur no more than four times a day, and (3) be at least 60 minutes between 

exposures [ACGIH 2016]. Additionally, ACGIH provides TLV-Ceiling values which are 

levels that should not be exceeded at any time during a work shift. 

OSHA requires an employer to furnish employees a place of employment free from 

recognized hazards that cause or are likely to cause death or serious physical harm 

[Occupational Safety and Health Act of 1970 (Public Law 91–596, sec. 5(a)(1))]. This is 

true in the absence of a specific OEL. It also is important to keep in mind that OELs may not 

reflect current health-based information. 

The results of the personal canister samples are compared to the OSHA PELs, NIOSH 

RELs, and ACGIH TLVs. Area samples for particles and TVOCs were collected to identify 

specific emission sources (3-D printers) and see how changes in processes or tasks influenced 

the characteristics of particles in the air. For all area samples of workplace air, it is not 

appropriate to compare results to these OELs. Note that for some measurements such as 

particle number, size, and surface area and TVOC concentration there are no recognized 

OELs to which the results can be compared to determine if they are safe. However, we 

included this data in our report so that the company can see how specific 3-D printing 

parameters and work tasks influence their release into workplace air. 

Results 

Objective 1: Evaluation of emissions during 3-D printing with PLA filament 

We collected samples in the Print Room to evaluate particle and chemical emissions from 

the 3-D printers under normal work conditions with PLA filament on two different days and 

overnight. During both days, objects were printed using white, black, dark blue, yellow, and/ 

or wood colored PLA filaments. Depending on the time of day, print job duration, and other 

factors, from 8 to 10 of the 3-D printers were in operation. 

Particle concentrations in the Print Room during the day 

The OPC and DC instruments used to monitor air in the Print Room were both placed at 

Location 2 (adjacent to the printers). The concentration of particles with sizes from 300 nm 

to greater than 20 μm did not exceed 100 particles per cubic centimeter of air (cm3

) on either 

day. Particle surface area concentration increased throughout the morning from about 50 

square millimeters of surface per cubic meter of air (mm2

/m3) to about 250 mm2/m3 by midday and decreased thereafter. 

CNC instruments were placed at both Location 2 (adjacent to the 3-D printers) and Location 

3 (just inside the door of the Print Room). On the first day, the number concentration of 

particles at both locations ranged from 50,000 to 200,000 particles/cm3

 of air (see Figure 2). 

A similar concentration pattern was observed on the second day. The high particle number 

concentrations measured with the CNC instruments compared to the OPC indicated that 
Health Hazard Evaluation Report 2017-0059-3291 Page 9 

 

particles emitted from the 3-D printers generally have small size. Note that on the first day, 

at Location 2, particle number concentration exceeded 450,000 particles/cm3

 of air on two 

occasions; these peaks at 144 minutes and 164 minutes corresponded to times when we 

placed the CNC monitor inlet near the open top of the same printer using white PLA. At 220 

minutes, we monitored that same printer, but when it was using black PLA, and there was no 

peak, which provided further evidence that white PLA was responsible for these increases in 

emitted particles. 

Figure 2. Particle number concentration in the Print Room while printing only with PLA 

filaments. The two peaks were from the same printer using white PLA. The arrow indicates 

the absence of a peak when that printer was using black PLA. 
Health Hazard Evaluation Report 2017-0059-3291

Figure 3 shows high magnification pictures of particles collected on filters in the Print Room 

and illustrate the small size of airborne particles released during 3-D printing with PLA 

filament. The particles are clusters of many small particles; the filter pores are the dark circles 

and the filter itself is the light gray background. Analysis of the particle chemistry determined 

that the particles were made up of iron and/or carbon which is typical of PLA emissions. 

Figure 3. High magnification images of particles (denoted by yellow arrows) emitted from a 

3-D printer while printing only with PLA filaments at Location 2 (left image) and Location 3 

(right image). Images by NIOSH. 

Figure 4 is a plot of particle size distribution measured in the Print Room on the first day 

using the NanoScan monitor. As shown in the plot, the average particle size is about 44 nm. 

On the second day, the average particle size was 40 nm. 

Figure 4. Particle size distribution in the Print Room while during the day while printing 

only with PLA filaments. The average particle size was about 44 nm. 

Page 10 
Health Hazard Evaluation Report 2017-0059-3291 Page 11 

Volatile organic chemical concentrations in the Print Room during the day 

We measured the real-time TVOC concentrations at both Location 2 and 3 (see Figure 5). On 

the first day, concentrations were initially about 2,000 micrograms (μg) per cubic meter of air 

(m3

) but increased to 12,000 μg/m3 at Location 2 and 9,000 μg/m3 at Location 3 as printers 

operated. At both locations, TVOC levels had a “saw tooth” pattern which is consistent 

with the starting and stopping of 3-D print jobs throughout the day. We observed similar 

concentration levels and patterns on the second day of monitoring. 

Figure 5. Total organic vapor concentrations in the Print Room while printing only with PLA 

filaments. 

We collected canister samples at both locations in the Print Room to identify and quantify 

individual organic chemicals. Table 2 summarizes the results of the canister samples. 

Generally, concentrations were similar between locations indicating that contaminants 

were mixed throughout the room. Acetaldehyde, acetone, ethanol, isopropyl alcohol, and 

toluene are known to be emitted during printing with PLA filaments [Stefaniak et al. 2017]. 

Though the canister method we used is not fully validated, the presence of diacetyl and 

2,3-pentanedione are of interest as these chemicals are often used as ingredients in flavorings 

and are known respiratory hazards [NIOSH, 2016]. Diacetyl and 2,3-pentanedione are 

types of chemicals referred to as “carbonyl” compounds which is a family of compounds 

with similar chemical structures. Based on our previous studies of 3-D printing, using 

experimental sampling methods, we determined that some chemicals emitted during printing 

can react with ozone in air to form carbonyl compounds [Stefaniak et al. 2017]. As such, it 

is likely that diacetyl and 2,3-pentanedione were not emitted by the printing process but were 

formed in air from the reaction of ozone and other organic chemicals. 
Page 12 Health Hazard Evaluation Report 2017-0059-3291

Table 2. Concentrations of organic chemicals in the Print Room while printing only 

with PLA filaments (all values in ppb) 

Location 2 Location 3 

Chemical Day 1 Day 2 Day 1 Day 2 

Acetaldehyde 46.2 23.9 40.1 18.7 

Acetone 93.5 114.9 110.7 92.5 

Benzene 3.5 

Diacetyl 1.0 0.5 2.9 

2,3-pentanedione 0.9 

Ethanol 21.4 21.8 16.0 

Isopropyl Alcohol 9525 16584 13621 14500 

Methyl Methacrylate 0.9 1.1 1.3 

Methylene Chloride 1.8 2.6 1.6 3.0 

Toluene 1.1 0.7 

m,p-Xylene 1.1 0.6 

Empty cell = chemical not detected 

Environmental conditions in the Print Room 

Environmental measurements were only made at Location 2. The average ozone 

concentration was 27 parts per billion (ppb) but reached a maximum of 60 ppb. Levels of 

carbon dioxide ranged from 600 parts per million (ppm) to 1300 ppm and levels of carbon 

monoxide were less than 2.5 ppm. Average temperature in the Print Room was 78 °F. 

Overnight Sampling in the Print Room 

At this facility, the 3-D printers were operated 24 hours a day. We monitored particles, 

TVOC concentrations, and environmental conditions in the Print Room during the overnight 

hours (approximately 6:00 pm to 10:00 am) on two occasions while the 3-D printers used 

PLA filaments. The purpose of this sampling was to determine if there was buildup of these 

contaminants in the Print Room overnight. 

We placed the OPC and DC instruments in the Print Room at Location 2. The concentration 

of particles with sizes from 300 nm to greater than 20 μm was less than 200 particles/cm3

 of 

air during either night. During both nights, particle surface area concentration decreased with 

time. We placed CNC instruments at Locations 2 (near the 3-D printers) and 3 (near the Print 

Room door). At both locations, particle number concentrations followed the same pattern and 

reached a maximum of 60,000 particles/cm3

 of air during the first night and 74,000 particles/ 

cm3

 during the second night. 

The TVOC concentration patterns at Locations 2 and 3 in the Print Room were the same 

during the overnight hours. During the first night, TVOC levels reached a maximum of 6,000 

μg/m3

 of air and during the second night TVOC levels reached 12,000 μg/m3 of air. 
Health Hazard Evaluation Report 2017-0059-3291 Page 13 

The maximum ozone concentration on either night was 62 ppb. Levels of carbon dioxide 

were below 1400 ppm, and carbon monoxide were less than 1.5 ppm. 

Objective 2: Evaluation of emissions during 3-D printing with ABS filament 

During this test, seven printers used PLA filaments (black, wood, or yellow) and three 

printers used ABS filament (white). As summarized in Table 3, during the time in which the 

three printers were operated with ABS and the other 7 were operated with PLA, there did not 

appear to be any difference in particle or chemical emissions compared to when all printers 

were operated with PLA on the prior days. All measurements were made at Location 2. 

Table 3. Maximum values for particles, vapors, and gases measured while printing with 

ABS and PLA filaments versus only PLA filaments 

Measurement 3 ABS/7 PLA 10 PLA 

Number of particles [0.3 to >20 μm], #/cm3 10 100 

Number of particles [20 to 1000 nm], #/cm3 80,000 200,000 

Size, nm 48 44 

Surface area of particles, mm2

/cm3 100 250 

Total organic chemicals, μg/cm3 15,000 12,000 

Ozone, ppb 55 60 

Carbon dioxide, ppm 1000 1300 

Carbon monoxide, ppm 1 2.5 

We collected canister samples at Locations 1 and 2 in the Print Room on the day in which 

printing was performed with both ABS and PLA filaments to identify and quantify individual 

organic chemicals. Table 4 summarizes the canister sampling results. Concentrations varied 

by location, and only half the chemicals were identified at both locations. Compared to Table 

2 (printing with PLA only), the identities and concentrations of chemicals were similar. One 

notable exception was the concentration of isopropyl alcohol. The high concentrations of 

isopropyl alcohol were likely not from the ABS filament. On this day, an intern was cleaning 

the build platform of a printer with isopropyl alcohol for approximately 40 minutes, which 

resulted in a higher concentration of this chemical in air. 
Page 14 Health Hazard Evaluation Report 2017-0059-3291

Table 4. Concentrations of organic chemicals in the Print Room while printing with 

ABS (3 printers) and PLA (7 printers) 

Concentration (ppb) 

Chemical Location 2 Location 3 

Acetaldehyde 26.7 21.8 

Acetone 146.3 157.4 

Diacetyl 1.4 0.5 

2,3-Pentanedione 1.2 0.6 

Ethanol 24.6 16.4 

Isopropyl Alcohol 34,050 18,425 

Methyl Methacrylate 0.8 1.2 

Methylene Chloride 1.5 2.5 

Toluene 1.5 1.8 

m,p-Xylene 0.8 0.6 

o-Xylene 0.3 

Empty cell = chemical not detected 

Objective 3: Determine if emissions from the Print Room infiltrate into the Engineer’s 

Office 

To evaluate if entrainment was occurring, we measured concentrations of particles and 

organic chemical in the Print Room and the Engineer’s Office using real-time monitors 

on each day and overnight. Table 5 summarizes the maximum concentrations of particles, 

organic chemicals, and gases measured in the Engineer’s Office and the Print Room over 

three days. Concentrations of particles with size 20 nm to 1000 nm in the Engineer’s Office 

were between 6,000 and 18,000/cm3

 on the first two days and up to 87,000/cm3 on the third 

day. As noted in the background section of this letter, the door to the Engineer’s Office was 

usually open to the High Bay, and this maximum particle concentration corresponded to the 

time during which grinding and injection molding were being performed in the High Bay. 

Levels of organic vapors and carbon dioxide were lower in the Engineer’s Office compared 

to the Print Room. The level of carbon monoxide was similar in the two rooms. 

Table 5. Maximum daytime values for particles, vapors, and gases in the Engineer’s 

Office and Print Room 

Print Room 

Measurement Engineer’s Office Location 2 Location 3 

Number of particles [20 to 1000 nm], #/cm3 87,000 450,000 270,000 

Total organic chemicals, μg/cm3 50,000 64,400 72,000 

Carbon dioxide, ppm 800 1800 1750 

Carbon monoxide, ppm 2 2.5 2 
Health Hazard Evaluation Report 2017-0059-3291 Page 15 

Figure 6 is a high magnification image of a particle collected on a filter in the Engineer’s 

Office that illustrates the large size of airborne particles in that room. Unlike the particles in 

the Print Room, this particle has a compact morphology. Analysis of the particle chemistry 

determined that it was composed of iron, calcium, magnesium, aluminum, and silica and 

is most likely sand or other naturally occurring dust that was brought into the facility from 

outside. 

Figure 6. High magnification image of a particle collected in the Engineer’s Office. Image by 

NIOSH. 

We also collected canister samples in the Engineer’s Office on each day and results are 

summarized in Table 6. Comparison of these results to Table 2 (PLA filaments) and Table 

4 (PLA and ABS filaments) reveals that five chemicals were common to the Engineer’s 

Office and the Print Room (acetaldehyde, acetone, ethanol, isopropyl alcohol, and toluene). 

Concentrations of acetaldehyde and isopropyl alcohol were relatively lower in the Engineer’s 

Office, but levels of acetone, ethanol, and toluene were similar. Six chemicals were 

identified and quantified in the Print Room (diacetyl, 2,3-pentanedione, methyl methacrylate, 

methylene chloride, m,p-xylene, and o-xylene) but not in the Engineer’s Office. 

Table 6. Concentrations of organic chemicals in the Engineer’s Office during three 

different days 

Concentration (ppb) 

Chemical Day 1 Day 2 Day 3 

Acetaldehyde 4.1 6.9 11.4 

Acetone 26.0 32.1 516.7 

Benzene 2.2 

Ethanol 17.4 16.0 26.5 

Isopropyl Alcohol 1376 2266 5723 

Toluene 2.3 1.0 

Empty cell = chemical not detected 
Page 16 Health Hazard Evaluation Report 2017-0059-3291

We measured levels of particles, organic chemicals, and gases overnight in the Engineer’s 

Office and the Print Room on two occasions (see Table 7). Concentrations of particles with 

size 20 nm to 1000 nm, and carbon dioxide levels in the Engineer’s Office were much lower 

than in the Print Room. Interestingly, TVOC levels were higher in the Engineer’s Office 

than in the Print Room on both nights. We were not present in the facility overnight so it 

is unknown what caused this increased concentration of organic vapors. Finally, levels of 

carbon monoxide were similar in all locations. 

Table 7. Maximum overnight concentration values for particles, vapors, and gases 

measured while printing with ABS and PLA filaments or PLA filaments only 

Print Room 

Measurement Engineer’s Office Location 2 Location 3 

Number of particles [20 to 1000 nm], #/cm3 11,230 74,900 61,900 

Total organic chemicals, μg/cm3 14,273 7,669 5,613 

Carbon dioxide, ppm 830 1478 1460 

Carbon monoxide, ppm 1.5 0.8 0.1 

Table 8 summarizes the canister sample results for the Engineer’s Office and the Print Room 

over two different nights. Eight chemicals were common to all locations, and except for 

toluene, levels were always higher in the Print Room. Six chemicals were identified and 

quantified in the Print Room but not in the Engineer’s Office. Three of these chemicals were 

carbonyl compounds (diacetyl, 2,3-hexanedione and 2,3-pentanedione). As mentioned 

previously, using experimental methods, it is believed that these compounds were formed by 

reaction of printer emissions with ozone, not emitted by the 3-D printers. 

Table 8. Maximum overnight concentrations of organic chemicals in the Engineer’s 

Office and Print Rooms 

Print Room 

Chemical Engineer’s Office Location 2 Location 3 

Acetaldehyde 7.4 36.9 26.7 

Acetone 42.2 163.5 137.3 

Benzene 0.8 

Diacetyl 13.3 5.2 

2,3-Hexanedione 4.1 

2,3-Pentanedione 6.0 3.5 

Ethanol 10.6 23.6 134.6 

Ethylbenzene 2.1 

Isopropyl Alcohol 6351 9504 9479 

Methyl Methacrylate 0.6 1.7 3.5 

Methylene Chloride 0.9 7.7 8.0 

Styrene 0.9 1.1 

Toluene 7.1 0.6 2.4 

m,p-Xylene 0.6 0.5 2.6 

o-Xylene 1.5 

Empty cell = chemical not detected 
Health Hazard Evaluation Report 2017-0059-3291 Page 17 

Objective 4: Effectiveness of the printer cover and doors to reduce emissions during 3-D 

printing 

We collected samples in the Print Room to evaluate whether the manufacturer-provided 

covers and doors of the 3-D printers are effective in reducing emissions. Throughout the 

day, objects were printed using black (7 printers), wood (2 printers), and yellow (1 printer) 

colored PLA filaments. Depending on the time of day, print job duration, and other factors, 

from 2 to 10 of the 3-D printers were in operation. 

Particles and organic chemicals in air were monitored in the Print Room under normal 

operating conditions from 11:00 am until 3:00 pm. The covers and doors provided by the 

3-D printer manufacturer were assembled and installed on all printers by 3:00 pm (see Figure 

7), and we continued to monitor particle and TVOC levels throughout the afternoon and 

overnight. 

Figure 7. 3-D printers as normally used (top picture) and with the manufacturer-provided 

plastic covers and doors installed (bottom picture). Photos by NIOSH. 
Page 18 Health Hazard Evaluation Report 2017-0059-3291

Particle concentrations in the Print Room 

During the first two hours of monitoring, only 2 to 6 printers were operating; thereafter, all 

10 printers were in use. At Location 2, particle concentration reached 275,000 particles/cm3 

of air when all 10 printers were in operation (see Figure 8). Approximately 4 hours after we 

began monitoring, all manufacturer-provided covers and doors were installed on the 3-D 

printers (time noted as a vertical line on Figure 8). Soon after installation, particle number 

concentration at Location 2 decreased, suggesting that the covers and doors helped to reduce 

particle levels in the Print Room; however, after 60 minutes, levels began to increase again. 

The same concentration pattern was observed at Location 3. 

Figure 8. Particle number concentration in the Print Room at Location 2 (adjacent to 3-D 

printers). The vertical line indicates the time at which all printer covers and doors were 

installed. 
Health Hazard Evaluation Report 2017-0059-3291 Page 19 

From visual inspection of the covers and doors, we observed that particles were adhering to 

the plastic. We determined that this temporary decline in number concentration was because 

emitted particles were adhering to the plastic covers and doors from electrostatic attraction 

(see Figure 9). Once this charge effect wore off, particle concentrations at Location 2 began 

to increase again (shown as rise in concentration at 300 minutes in Figure 8). 

Figure 9. Particle emitted by the 3-D printers initially deposited on the manufacturerprovided covers and doors. Photo by NIOSH. Arrows point to examples of adhered 

particles. 

Approximately 80 minutes after the covers and doors were installed on the printers, we 

placed the inlet to the CNC real-time monitor above the 3-D printers near the rear of the 

cover which was open to the room. Particle number concentration was measured twice for 

each printer over a period of 60 minutes. In general, the number concentration measured 

among all printers was between 150,000 particles/cm3

 and 200,000 particles/cm3 of air which 

is essentially unchanged from the airborne concentrations measured in the Print Room before 

the covers and doors were installed (see Figure 8 for comparison). 

We also used the CNC monitor to measure the number of particles when the door installed on 

the printer was opened and when the cover was removed. Particle number concentration was 

measured twice for each printer (once with the door open, once with the cover removed) over 

a period of 60 minutes (see Figure 10). For some printers, there was an increase in number 

concentration when the door was opened or cover removed, though in general the number 

concentration measured among all printers was about 100,000 particles/cm3

 of air which 

is similar to the airborne concentrations measured in the Print Room before the covers and 

doors were installed (see Figure 8 for comparison). 
Page 20 Health Hazard Evaluation Report 2017-0059-3291

Figure 10. Particle number concentration in the Print Room when printer doors were opened 

or covers removed. 

At Location 2, the concentrations of particles with sizes from 300 nm to greater than 20 

μm were below 100 particles/cm3

 during the day. The particle surface area concentration 

decreased slightly when the printer covers and doors were installed but increased again 

shortly thereafter. 

Finally, from the NanoScan monitor, the average particle size during the day was 38 nm 

which was similar to the average size measured without the doors and covers in place (44 

nm). The NanoScan measurements followed the same pattern as the CNC instrument (see 

Figure 8); i.e., there was a temporary decline in particle number concentration just after 

installation of the covers and doors on the printers, but concentrations soon returned to the 

same levels as before installation. 
Health Hazard Evaluation Report 2017-0059-3291

Volatile organic chemical concentrations in the Print Room 

The TVOC concentrations at Locations 2 and 3 in the Print Room were similar during the 

day. As shown in Figure 11, at Location 2, the TVOC concentrations did not appear to be 

influenced by the printer covers and doors. 

No covers or doors 

Figure 11. Total volatile organic compound concentration in the Print Room at Location 2 

(adjacent to 3-D printers). The vertical line indicates the time at which all printer covers and 

doors were installed. 

Environmental conditions in the Print Room 

Ambient carbon dioxide (range: 600 to 1400 ppm), carbon monoxide (less than 1 ppm), and 

ozone (less than 70 ppb) concentrations varied only slightly during the day. 

Overnight Sampling in the Print Room 

We monitored particles, TVOC concentrations and environmental conditions in the Print 

Room during the overnight hours (approximately 6:30 pm to 9:00 am) while the 3-D 

printers operated with the manufacturer-provided doors and covers in place. At Location 

2, the concentration of particles with sizes from 0.3 to greater than 20 μm measured by the 

OPC were below 10 particles/cm3

 throughout the night. Particle surface area concentration 

measured by the DC decreased during first 2 hours and remained at a steady low 

concentration overnight. Particle number concentration increased to almost 75,000 particles/ 

cm3

 in the Print Room early on in the night but decreased thereafter to about 2,000 particles/ 

cm3

 by midnight. At about 12:30 am, particle concentration increased to about 16,000 

particles/cm3

 and remained elevated for the next 5.5 hours before it decreased to about 1,000 

Page 21 
Page 22 Health Hazard Evaluation Report 2017-0059-3291

particles/cm3 for the remainder of the night. We were not present at the facility during the 

night, though one possible explanation for the observed pattern is that particle concentrations 

increased early on in the evening when all printers were in operation but decreased as print 

jobs were completed. In discussions with the owner, he sometimes comes into the facility 

late at night to start new print jobs, and this could explain the increase in particle number 

concentration beginning about 12:30 am. 

TVOC concentrations in the Print Room increased to a maximum of about 12,000 μg/m3

 of 

air by midnight, and decreased thereafter for the remainder of the night. Ozone concentration 

remained below 50 ppb overnight. Carbon dioxide was less than 1,400 ppm at all times, and 

carbon monoxide was less than 1 ppm at all times throughout the night. 

Though the observed decreases in particle number and TVOC concentrations throughout 

the night could be attributed to effectiveness of the printer covers and doors, based on the 

daytime sampling results (Figures 8 and 11), it is more likely that the declines are because 

fewer printers operated throughout the night as print jobs were finished. 

Objective 5: Effectiveness of a ventilated enclosure to reduce particle and chemical 

levels in the Print Room 

We collected samples in the Print Room to evaluate whether a ventilated enclosure system 

with filtration was effective in reducing particle and organic vapor levels in the Print Room. 

The enclosure was custom-built by NIOSH based on dimensions of the shelving units used 

to hold the 3-D printers. As shown in Figure 12, the enclosure consisted of acrylic panels for 

doors that were held closed using magnetic strips. The enclosure was then ventilated using 

a portable floor fan (Model SS-400-PYT, Sentry Air Systems Inc., Houston, TX) connected 

to 6-inch diameter flexible hose (Model W1036, Woodstock International Inc., Bellingham, 

WA) to exhaust the air around the printers. The portable floor fan had a variable speed 

controller rated to move air at up of 700 cubic feet per minute (CFM) and the air was passed 

through a high efficiency particulate air (HEPA) filter (Model SS-400-HF, Sentry Air Systems 

Inc., Houston, TX) and an 8 lb carbon bed (Model SS-408-CF, Sentry Air Systems Inc., 

Houston, TX) to remove particles and organic vapors, respectively before discharging the air 

back into the room. 

In the morning, seven printers used PLA filaments (black, wood, or yellow). Starting at 1:50 

p.m., four printers used ABS filament (white) and six used PLA filament (wood, black, and 

yellow). Particles and organic chemicals in air were monitored in the Print Room from 9:00 

a.m. until 7:00 p.m. (printer covers and doors in place). The enclosure doors were installed 

on the shelves by 10:15 am but were not closed until 11:45 am. We continued to monitor 

particle and TVOC levels throughout the afternoon and overnight. 
Health Hazard Evaluation Report 2017-0059-3291 Page 23 

Figure 12. Custom-built ventilated enclosure connected to a floor fan with particle and 

organic filters. Photo by NIOSH. 
Page 24 Health Hazard Evaluation Report 2017-0059-3291

Particle concentrations in the Print Room 

During the day, the enclosure doors were closed, and the fan turned on to ventilate the 

printers three different times. The first test was from 11:45 am to 12:12 pm, the second test 

was from 1:50 pm to 2:15 pm, and the third test from 3:22 pm to 4:48 pm. Particle number 

concentration measured using the OPC remained below 50/cm3

 of air throughout the day. 

Figure 13 is a plot of particle number concentration measured by the NanoScan monitor in 

the Print Room. Particle concentration in the room decreased each time the enclosure doors 

were sealed and the fan turned on but rose again as soon as the doors were opened and the 

fan turned off. The average particle size was 55 nm which was slightly larger than measured 

on the previous days in the Print Room. Similar patterns were observed for number 

concentration measured using the CNC monitor and surface area concentration measured 

using the DC at Location 2. 

Figure 13. NanoScan measurements of particle number concentration in the Print Room 

illustrating that levels decreased each time the enclosure doors were sealed and the fan turned 

on but increased when the enclosure was not used. Vertical red lines indicate when enclosure 

doors were sealed and the fan turned on. Vertical black lines indicate when doors were 

opened and the fan turned off. Gap in data from 193 to 279 minutes is when the NanoScan 

was moved from the Print Room to the High Bay. 
Health Hazard Evaluation Report 2017-0059-3291 Page 25 

Volatile organic compound concentrations in the Print Room 

As shown in Figure 14, TVOC concentrations at Location 2 decreased each time the 

enclosure doors were closed and the fan turned on to ventilate the printers. TVOC 

concentrations at Location 3 followed a nearly identical pattern to that shown in Figure 14, 

and concentration values were very similar. During the day, an intern cleaned the build plate 

on a 3-D printer using 91% isopropyl alcohol. The cleaning began at 227 minutes and is 

noted in Figure 15. The cleaning task lasted about 30 minutes. After cleaning, the alcohol 

bottle was capped, but the sponge used for cleaning was left beside the printer for about 10 

minutes before it was removed from the Print Room. After removing the sponge, there was a 

visible wet residue on the shelf. 

Figure 14. Total volatile organic chemical measurements in the Print Room illustrating 

the effectiveness of the ventilated enclosure to reduce levels during use. Vertical red lines 

indicate when enclosure doors were sealed and the fan turned on. Vertical black lines indicate 

when doors were opened and the fan turned off. 

Environmental conditions in the Print Room 

Ozone concentrations were 70 ppb throughout the day. Carbon dioxide concentrations at 

Locations 2 and 3 were nearly identical and ranged from 1,000 to 1,800 ppm throughout the 

day. Carbon monoxide levels were less than 4 ppm during the day. Ozone, carbon dioxide, 

and carbon monoxide concentrations were not influenced by use of the ventilated enclosure. 

Overnight Sampling in the Print Room 

We monitored particle number concentration and TVOC concentration inside the 

enclosure while it was ventilating the printers and outside the enclosure (at Location 2) 

from approximately 6:00 pm until 9:00 am the next day. Additionally, particle size was 

measured in the Print Room using the NanoScan monitor. During this time, all 3-D printers 

were operating with the doors and covers in place. Outside of the enclosure, the particle 
Page 26 Health Hazard Evaluation Report 2017-0059-3291

number concentration measured using the CNC monitor reached 142,000/cm3 of air in 

the Print Room before the doors were sealed and the fan turned on. Within 30 minutes of 

turning on the fan, the particle number concentration in the room decreased to 418/cm3

 of 

air which is a 99.7% reduction in particle concentration in the room (see Figure 15). From 

the NanoScan monitor, the average particle size outside the enclosure was 40 nm, and the 

reduction of particle number concentration was 99.7%. Inside the enclosure, particle number 

concentration peaked at 261,000/cm3

 of air and decreased to 4,050/cm3 of air within 50 

minutes which is a 98.4% reduction in particle concentration. 

Figure 15. Particle number concentration in the Print Room outside the ventilated enclosure. 

Vertical line indicates when the enclosure doors were sealed and the fan turned on. 
Health Hazard Evaluation Report 2017-0059-3291 Page 27 

Figure 16 is a plot of total volatile organic chemical concentration in the Print Room outside 

the ventilated enclosure. The real-time instrument turned off after monitoring for 4 hours, 

though during that time, the organic vapor concentration decreased 53.2%. Inside the 

enclosure, the real-time instrument ran for 7 hours before turning off and during that time, the 

organic vapor concentration decreased by 69.5%. 

Figure 16. Total volatile organic chemical concentration in the Print Room outside the 

ventilated enclosure. Vertical line indicates when the enclosure doors were sealed and the fan 

turned on. 
Health Hazard Evaluation Report 2017-0059-3291

Objective 6: Evaluation of post-processing tasks and injection molding in the High Bay 

Post-processing tasks were evaluated on two different days in the High Bay. On the one day, 

printed objects were briefly sanded, torched using a butane torch, and one object was stained 

using polyurethane. On the other day, injection molding with ABS pellets and sanding of 

printed objects were performed. 

On the day that sanding, torching, and staining were performed, the tasks collectively lasted 

approximately 40 minutes. Particle concentrations measured using the OPC and CNC did not 

differ from background concentrations measured in the High Bay when no tasks were being 

performed. Average background concentration measured using the NanoScan was about 7200 

particles/cm3

 of air, but levels reached 11,000 to 15,000 particles/cm3 of air during sanding 

(on the other day that sanding was performed, concentrations reached 30,000 particles/cm3

 of 

air). Total volatile organic chemical concentrations during background were about 5,000 μg/ 

m3

 and fluctuated during post-processing tasks such as light torching. Levels rose to 26,000 

μg/m3

 during polyurethane staining (see Figure 17). 

Using polyurethane 

Figure 17. Total volatile organic chemical concentration in the High Bay during postprocessing task. 

Page 28 
Health Hazard Evaluation Report 2017-0059-3291 Page 29 

Figure 18 is a plot of particle number concentration measured using the NanoScan instrument 

during injection molding. During warm-up of the injection molding machine, a reservoir 

containing ABS pellets was heated from 40 °C to 235 °C, and particle number concentration 

rapidly increased from an average background level of 3,400 particles/cm3

 to over 134,000 

particles/cm3

. Next, the employee injection molded six parts; particle number concentration 

was increased above background and ranged from 20,000 particles/cm3

 to 26,000 particles/ 

cm3

 during this task. At one point, the employee used a rotary grinding wheel to hone a 

scraper, and the number concentration increased to over 56,000 particles/cm3

. We observed 

that during grinding the employee did not use eye protection. 

Figure 18. Particle number concentration in the High Bay during injection molding 

illustrating an increase in particles during warm-up of the molding machine and during 

grinding. 

Organic chemical concentrations were measured using the TVOC monitor and 450 ml 

evacuated canisters. From the real-time TVOC monitor data, there was no appreciable 

change in concentration during injection molding or opening a mold; however, concentration 

increased from about 4,000 μg/m3

 to over 72,000 μg/m3 when ABS pellets were added to the 

pre-heated hopper. The canister samples were collected over a period of 10 to 15 seconds 

during specific tasks. 

Table 9 summarizes the concentrations of individual VOCs measured using canisters 

positioned adjacent to the injection molding machine at the start of warm-up (40 °C) and 

when the machined reached its set temperature (235 °C). Additionally, a canister sample 

was collected at the opening to the hopper used to feed ABS pellets into the machine 
Page 30 Health Hazard Evaluation Report 2017-0059-3291

about 10 minutes after reaching the set temperature. All measurements were corrected for 

the background concentrations of these chemicals in High Bay room air when tasks were 

not performed. The identities and concentrations of VOCs were similar during warm-up; 

however, at the hopper opening more VOCs were identified and at higher concentrations. 

Table 9. Concentrations of organic chemicals in the High Bay during warm-up of the 

injection molding machine 

Chemical Start (40 °C) Set point (235 °C) Hopper opening 

Acetaldehyde 2.6 56.7 

Acetone 87.3 

Benzene 103.2 

Diacetyl 0.1 0.8 

2,3-Hexanedione 

2,3-Pentanedione 0.5 0.6 

Ethanol 19.4 15.6 33.5 

Ethylbenzene 7.6 

Isopropyl Alcohol 524.4 530.5 2161 

Methyl Methacrylate 0.2 27.0 

Methylene Chloride 

Styrene 22.7 

Toluene 3.9 

m,p-Xylene 0.2 0.7 

o-Xylene 0.8 

Empty cell = chemical not detected 
Health Hazard Evaluation Report 2017-0059-3291 Page 31 

The molding machine was equipped with a plastic safety shield to prevent a person 

from placing their hand in the area of the die during molding. Table 10 summarizes the 

concentrations of individual VOCs measured using canisters positioned inside (samples 1 - 4) 

and outside (samples 1 - 2) of this shield while molding parts with ABS thermoplastic. Four 

chemicals were common to samples collected inside and outside of the shield (acetaldehyde, 

acetone, ethanol, and isopropyl alcohol), but only the measured concentrations of acetone 

were higher inside the shield. Ten different chemicals were quantified (all at low levels) 

inside the shield but not detected outside of the shield. Four of these chemicals, ethylbenzene, 

styrene, m,p-xylene, and o-xylene have been identified in emissions from 3-D printing with 

ABS filaments [Stefaniak et al. 2017]. 

Table 10. Concentrations of organic chemicals inside (samples 1 – 4) and outside 

(samples 5 and 6) of the injection molding machine safety shield 

Inside shield Outside shield 

Chemical Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 

Acetaldehyde 9.0 6.2 33.1 0.4 

Acetone 46.1 6.4 9.5 6.1 

Benzene 0.6 2.3 

Diacetyl 1.0 

2,3-Hexanedione 

2,3-Pentanedione 1.3 

Ethanol 24.1 16.6 22.6 28.1 23.7 39.6 

Ethylbenzene 0.5 

Isopropyl Alcohol 1245 2700 2907 14920 12060 10684 

Methyl Methacrylate 0.4 0.7 0.2 

Methylene Chloride 0.5 

Styrene 2.1 1.0 

Toluene 1.0 

m,p-Xylene 0.6 0.2 0.5 

o-Xylene 0.5 

Empty cell = not detected 
Health Hazard Evaluation Report 2017-0059-3291

Objective 7: Employee exposures to volatile organic chemicals 

As shown in Figure 19, personal TVOC exposures were usually below 15,000 μg/m3

 of 

air on all days and consisted of intermittent periods of relatively low exposure and high 

exposure. While we did not observe all movements of the Engineer throughout the days, 

some segments of exposure can be assigned to specific events. For example, at the start of 

shift on Day 3 the TVOC exposure reached almost 30,000 μg/m3

, but this occurred when an 

intern used isopropyl alcohol in the Print Room to clean a printer. Another example is on Day 

2, when the Engineer used polyurethane to stain a part in the High Bay which resulted in an 

exposure to organic chemicals from the coating. 

Isopropyl alcohol 

used in Print Room 

Used polyurethane 

Figure 19. Personal exposures to total volatile organic chemicals during work on three 

different days. 

Table 11 summarizes the identities and concentrations of individual VOCs measured in 

the breathing zone of the Engineer on each day of the site visit (sample collection ranged 

from 3 hours to 6.5 hours among days). Acetone and isopropyl alcohol were measured on 

all days; whereas, acetaldehyde and m,p-xylene were measured on two of three days, and 

the remaining chemicals quantified on a single day. Among the chemicals identified, the 

concentration of isopropyl alcohol was the highest on all days. As shown in Figure 19, there 

was a large increase in TVOC concentrations on Day 3 when isopropyl alcohol was used to 

clean a printer and that day was also the highest personal exposure to this chemical. Table 11 

also includes OELs for the individual chemicals that were measured in the breathing zone of 

the Engineer. Measured concentrations of all chemicals were well below their corresponding 

OEL values. Note that if more printers were used in the Print Room or other changes were 

made to existing work practices, it could increase exposure levels. 

Page 32 
Health Hazard Evaluation Report 2017-0059-3291 Page 33 

 

Table 11. Personal exposures to volatile organic chemicals 

Concentration (ppm) 

Chemical Day 1 Day 2 Day 3 PEL REL TLV® 

Acetaldehyde 0.02 0.01 200 Carca 25b 

Acetone 0.05 0.04 0.11 1000 250 250 

Diacetyl 

2,3-Hexanedione 

2,3-Pentanedione 

Ethanol 0.05 1000 1000 1000c 

Isopropyl Alcohol 

Methyl 

Methacrylate 

Methylene Chloride 

2.6 

0.002 

2.0 8.8 

0.0004 

400 

100 

25 

400 

100 

Carca 

200 

50 

50 

Toluene 0.0009 200 100 20 

m,p-Xylene 0.002 0.0005 100 100 100 

Empty cell = chemical not detected; carc=carcinogen.
 a

 NIOSH recommends that careful consideration should be given to reducing exposures to carcinogens.
 b

 Ceiling value that should not be permitted to exceed.
 c

 Short-term exposure limit (STEL) 

Employees did not report any respiratory symptoms or other symptoms associated with their 

work. 

Discussion 

During the first two days of our site visit, we collected samples in the Print Room to evaluate 

particle and chemical emissions from the 3-D printers under normal work conditions with PLA 

filaments. During both days, objects were printed using white, black, dark blue, yellow, and/ 

or wood colored PLA filaments. In general, the number concentration of particles ranged from 

50,000 particles/cm3

 to 200,000 particles/cm3 of air (see Figure 2) but increased to 450,000 

particles/cm3

 of air when printing when using white PLA filament. We have previously 

evaluated emissions from 3-D printers in a test chamber and observed that some filament colors 

emit higher levels of particles than others even when made by the same manufacturer [Yi et al., 

2016]. The reason why emissions differ by color is not fully understood at this time but may be 

due to the additives used for coloring the plastics. 

On the day during which objects were printed using both ABS and PLA filaments, there was 

no appreciable difference in measured emissions compared to using only PLA filaments. In our 

chamber testing, we have observed higher particle emissions from ABS relative to PLA [Yi 

et al., 2016]. In an early study of 3-D printers, Stephens and colleagues reported that printing 

with ABS increased particle levels in a room relative to when operating with PLA filaments 

[Stephens et al., 2013]. Several VOCs were released during printing with PLA filaments (see 

Table 2), and the same chemicals were also measured at similar concentrations when printing 

with ABS filaments (see Table 4). In chamber tests of 3-D printers, we observed that printing 
Page 34 Health Hazard Evaluation Report 2017-0059-3291

 

 

with ABS but not PLA filaments emitted ethylbenzene, styrene, m,p-xylene, and o-xylene 

[Stefaniak et al., 2017]. In the Print Room, m,p-xylene was measured when printing with 

both types of filaments, but o-xylene was only measured when printing with ABS filaments. 

The absence of styrene in canister samples collected in the Print Room on the day that ABS 

filaments were used is notable because this chemical is a component of the filament. We only 

evaluated printing when up to four devices were using ABS filament. If more printers are 

operated using ABS filament, it could change the types and levels of particle and chemical 

emissions. 

While we were on site, the owner expressed interest in understanding whether emissions 

from the 3-D printers were escaping from the Print Room and entering the Engineer’s Office. 

As noted in the background section of this report, these rooms were separated by a wall that 

reached up to a drop ceiling but did not extend to the building ceiling. Based on the differences 

in particle concentration profiles, particle morphology and chemistry, and organic chemical 

identities and concentrations between the two locations (see Figure 6 and Tables 5 – 8), it does 

not appear that emissions from the 3-D printers were being entrained into the Engineer’s Office. 

On the second day of our site visit, the plastic covers and doors that were provided by the 

printer manufacturer were assembled and installed on the 3-D printers. Though it initially 

appeared that the covers and doors might help to reduce particle (see Figure 8) and chemical 

(see Figure 11) concentrations in the Print Room, air monitoring after their installation 

demonstrated that they were not effective. These covers and doors were likely designed and 

intended to maintain a uniform temperature in the build space. As such, it is important to be 

aware that their use will not control emissions. 

Next, we evaluated whether a custom-built ventilated enclosure (see Figure 12) could reduce 

particle and chemical emissions in the Print Room. As shown in Figures 13 -16, this enclosure 

system was highly effective in reducing both particle number and TVOC concentrations in 

the Print Room. As noted at the beginning of the Results section of this report, there are no 

occupational exposure limits for particle number concentration or TVOC levels. As such, it 

is unknown at this time whether the measured levels present a health hazard and whether the 

reported reductions in contaminant levels are necessary. However, if improved ventilation is 

desired, one possible consideration would be to route the exhaust from the NIOSH custom 

enclosure to a fan on the roof at 700 cubic feet per minute to discharge the particle and volatile 

emissions from the 3-D printing process to the outdoors away from outdoor air intakes. This 

option would create the need for make-up air to be supplied inside the room but outside of the 

NIOSH custom enclosure. Also, similar capture effectiveness could be achieved at a lower air 

flow rate by sealing air gaps around the NIOSH custom enclosure. 

We evaluated various post-processing tasks as well as injection molding with ABS pellets. 

During sanding of 3-D printed objects, particle concentrations were relatively low and released 

particles were generally on the order of several micrometers. For injection molding, two tasks 

resulted in elevated emissions: warm-up and adding pellets to the machine hopper. There was 

no appreciable change in particle or TVOC concentrations during injection molding or opening 

of the mold. During warm-up, the molding machine reservoir which contained plastic pellets 
Health Hazard Evaluation Report 2017-0059-3291 Page 35 

 

 

 

was heated from 40 °C to 235 °C to melt the plastic and particle number concentration in the 

High Bay rapidly increased from an average background level of 3,400 particles/cm3

 to over 

134,000 particles/cm3

 (see Figure 18). 

In a study of 3-D printers, Deng and colleagues determined that particle emissions were mostly 

from the heating process during warm-up of the extruder nozzle rather than the printing process 

because the plastic filament undergoes decomposition during the heating period after being 

loaded into the extruder [Deng et al., 2016]. The heating process for 3-D printers is analogous 

to the heating process for the injection molding machine. In both devices, thermoplastic 

(filament in the case of 3-D printers, pellets in the case of injection molding) is heated to melt 

it. The higher the set-point temperature, the longer the filament must be heated, and the more it 

will break down to release particles and organic chemicals. 

When ABS pellets were added to the pre-heated injection molding machine, TVOC 

concentrations increased from a background level of about 4,000 μg/m3

 to over 72,000 μg/m3. 

Analysis of canister samples indicates that the major organic chemical present during injection 

molding with ABS plastic was isopropyl alcohol; however, low levels of ethylbenzene, styrene, 

m,p-xylene, and o-xylene were also measured. In chamber tests of 3-D printers using ABS, 

we have measured these same four chemicals but have not detected them in emissions while 

printing with PLA filaments [Stefaniak et al. 2017]. 

Personal exposures to organic chemicals were very low. The highest measured personal 

exposure was for isopropyl alcohol and this level was more than 20 times below the 

lowest applicable OEL. It is important to note that while diacetyl, 2,3-pentanedione and 

2,3-hexanedione were identified in general area air samples, indicating a potential exposure 

risk, none of these carbonyl compounds were detected on personal exposure samples. 

Exposures to organic chemicals cannot be attributed solely to 3-D printing because the 

Engineer is mobile and spends time in the Print Room, Engineer’s Office, and the High Bay. 

As demonstrated in Figure 19, some exposure can be attributed to cleaning printers or postprocessing tasks. 

Finally, it is important to note that the measured personal exposures and workplace emissions 

are a reflection of current working conditions. It is known from existing research that 3-D 

printer- and filament-related factors influence emissions [Yi et al., 2016; Stefaniak et al., 

2016]. Changes in printer parameters such as the thickness of each printed layer, the extrusion 

temperature, build plate temperature, filament feed rate, and number of printers can all 

influence emissions. Filament properties such as ingredients, inclusion of additives, type (for 

example, ABS or PLA), and color can also influence emissions. As such, if changes are made 

to how desktop 3-D printing is performed or which filaments are used or if the industrial-scale 

3-D printer is used, they will likely change the emissions and personal exposures. 

Conclusions 

Employees were exposed to detectable levels of organic chemicals in the air while working 
Page 36 Health Hazard Evaluation Report 2017-0059-3291

in this facility, though not all exposures were from 3-D printing. All measured personal 

exposures to organic chemicals were well below applicable OSHA PELs. We recommend 

that if changes are made to the existing process or if the industrial-scale 3-D printer is put 

into use, the employer should reassess personal exposures and emissions. Employees should 

be aware of how specific tasks influence exposures and that changes in how they perform 

their work could increase exposure. At this time, we do not recommend any controls to lower 

exposures as they are already well-below established regulatory limits. Similarly, at this time 

we do not recommend the need to lower total particle number and TVOC concentrations as 

there is no available guidance on an appropriate level; however, as shown in this report, these 

measurements are useful for understanding how various printing parameters and work tasks 

can influence the amount of particles and chemicals that get into air. Additionally, the realtime measurements in this report can be used as a reference to which particle and chemical 

levels can be compared if operations are expanded or modified in the future. It is important to 

note that 3-D printing has not been thoroughly evaluated to determine its safety. As such, new 

information may become available in the future which may change our current perspective 

on the necessity of controls. 

Recommendations 

On the basis of our findings, we recommend the actions listed below. We encourage this 3-D 

printing facility to use a labor-management health and safety committee or working group to 

discuss our recommendations and develop an action plan. 

Our recommendations are based on an approach known as the hierarchy of controls. This 

approach groups actions by their likely effectiveness in reducing or removing hazards. In 

most cases, the preferred approach is to eliminate hazardous materials or processes and 

install engineering controls to reduce exposure or shield employees. Until such controls 

are in place, or if they are not effective or feasible, administrative measures and personal 

protective equipment may be needed. 

Elimination and Substitution 

Eliminating or substituting hazardous processes or materials reduces hazards and protects 

employees more effectively than other approaches. Prevention through design, considering 

elimination or substitution when designing or developing a project, reduces the need for 

additional controls in the future. 

1. Based on our measurement results, we do not have any recommendations to eliminate 

or substitute filament materials at this time; however, if changes are made to the 3-D 

printing process or which filaments are used it would be prudent to reassess emissions 

and personal exposures. 
Health Hazard Evaluation Report 2017-0059-3291 Page 37 

Engineering Controls 

Engineering controls reduce employees’ exposures by removing the hazard from the process 

or by placing a barrier between the hazard and the employee. Engineering controls protect 

employees effectively without placing primary responsibility of implementation on the 

employee. 

1. At this time, we do not recommend any controls to lower chemical exposures as they 

are already well-below established regulatory limits. Similarly, at this time we do not 

recommend the need to lower total particle and TVOC concentrations. 

2. If the employer wanted to utilize a ventilated enclosure such as the one we tested, the 

details of its construction are provided in this report. 

Administrative Controls 

The term administrative controls refers to employer-dictated work practices and policies 

to reduce or prevent hazardous exposures. Their effectiveness depends on employer 

commitment and employee acceptance. Regular monitoring and reinforcement are necessary 

to ensure that policies and procedures are followed consistently. 

1. At this facility, it is normal practice to keep the Print Room door closed, and we 

recommend continuing this practice. Additionally, we recommend that employees 

close the door to the Engineer’s Office when performing tasks that generate dusts and 

organic chemicals in the High Bay. 

Personal Protective Equipment 

Personal protective equipment is the least effective means for controlling hazardous 

exposures. Proper use of personal protective equipment requires a comprehensive program 

and a high level of employee involvement and commitment. The right personal protective 

equipment must be chosen for each hazard. Supporting programs such as training, changeout schedules, and medical assessment may be needed. Personal protective equipment should 

not be the sole method for controlling hazardous exposures. Rather, personal protective 

equipment should be used until effective engineering and administrative controls are in place. 

1. We observed that during grinding the employee did not use eye protection and 

recommend the use of appropriate protective eyewear when performing this task. 
Page 38 Health Hazard Evaluation Report 2017-0059-3291

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Health Hazard Evaluation Report 2017-0059-3291 Page 41 

Keywords: NAICS 323111 Texas, 3D printer, nanoparticles, volatile organic compounds, 

acrylonitrile butadiene styrene, poly lactic acid. 
Page 42 Health Hazard Evaluation Report 2017-0059-3291

The Health Hazard Evaluation Program investigates possible health hazards in the workplace 

under the authority of the Occupational Safety and Health Act of 1970 (29 U.S.C. § 669(a) 

(6)). The Health Hazard Evaluation Program also provides, upon request, technical assistance 

to federal, state, and local agencies to investigate occupational health hazards and to prevent 

occupational disease or injury. Regulations guiding the Program can be found in Title 42, Code 

of Federal Regulations, Part 85; Requests for Health Hazard Evaluations (42 CPR Part 85). 

Disclaimer 

The recommendations in this report are made on the basis of the findings at the workplace 

evaluated and may not be applicable to other workplaces. 

Mention of any company or product in this report does not constitute endorsement by the 

National Institute for Occupational Safety and Health (NIOSH). 

Citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in this document were accessible as 

of the publication date. 

Acknowledgments 

Desktop Publisher: Tia McClelland 

Data Analysis Support: Brian Tift 

Laboratory Support: Ryan LeBouf, Dru Burns 

Site Visit Team Members: Duane Hammond, Alyson Johnson, Aleksandr Stefaniak 

Availability of Report 

Copies of this report have been sent to the employer, employees, and union at the 

facility. The state and local health department and the Occupational Safety and Health 

Administration Regional Office have also received a copy. This report is not copyrighted and 

may be freely reproduced. 

This report is available at http://www.cdc.gov/niosh/hhe/reports/pdfs/2017-0059-3291.pdf. 

All other HHE Reports may be found at http://www2a.cdc.gov/hhe/search.asp 

Recommended citation for this report: 

NIOSH [2017]. Health hazard evaluation report: evaluation of 3-D printer emissions 

and personal exposures at a manufacturing workplace. By Stefaniak AB, Hammond 

D, Johnson AR, Knepp AK, LeBouf RF. Morgantown, WV: U.S. Department of Health 

and Human Services, Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health, NIOSH HHE Report No. 2017-0059-3291 

Health Hazard Evaluation Report 2017-0059-3291 
Delivering on the Nation’s promise:

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To receive documents or other information about 

occupational safety and health topics, contact NIOSH 

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or visit the NIOSH website at http://www.cdc.gov/niosh