particles). NIOSH researchers identified 

the need for a device to collect

representative samples of airborne 

nanoparticles for the purpose of

conducting microanalyses such as

TEM and EDS. NIOSH mine safety

researchers therefore collaborated with 

colleagues at the NIOSH

Nanotechnology Research Center to 

develop an electrostatic precipitator (ESP) 

nanoparticle sampler [Miller et al. 2010a].

ESP Nanoparticle Technology

The handheld ESPnano (Figure 1) is 

battery-powered and encased in a

rugged enclosure. It comes with

Need for Airborne Particle Sampling

Mine workers are exposed to a variety of 

hazardous airborne particles that can lead 

to respiratory illness, and researchers from 

the National Institute for Occupational 

Safety and Health (NIOSH) study ways to 

mitigate exposures to such particulate 

matter. Due to rapid advances in nanotechnology, researchers have recently

focused on the role of airborne ultrafine 

and nano-sized particles in harming

workers’ health. The smallest of these

particles are easily inhaled and not

effectively filtered by the nose or upper 

respiratory system, allowing them to 

deeply penetrate the lungs. Inhalation 

of these particles can be associated with 

respiratory illness, cardiovascular disease, 

and lung cancer, which can have a long 

latency period, extending into decades. 

Further, these illnesses and diseases may 

be asymptomatic, with negative physical 

effects remaining hidden until

diagnosed, and can thus affect a person’s quality of life and reduce their 

life span. Respiratory disease therefore 

continues to be one of the single biggest 

occupational health hazards in mining.

By definition, research on airborne

hazards involves detailed particle

analyses, and while many devices exist 

to measure airborne particle concentrations, a technology gap existed when 

taking samples for detailed

physico-chemical characterization and 

particle speciation (e.g., differentiating 

between welding fume and dust

Summary

The commercially available ESPnano particle 

sampler allows industrial hygienists and 

safety professionals to easily take air samples 

that can be used to attain detailed particle 

information via micro-analytical techniques 

such as transmission electron microscopy 

(TEM), scanning electron microscopy (SEM), 

and energy dispersive spectrometry (EDS). 

The ESPnano collects representative samples 

of inhalable, respirable, and submicron 

particles for offline analyses. The instrument 

is being used worldwide for both research and 

workplace assessments of airborne hazards.

By Arthur Miller, PhD

Grant King, ME

No. 562 February 2020

Milestones in Mining Safety and Health Technology

NIOSH MINING PROGRAM

Technology News

Figure 1: Inserting a “sampling key” into the ESPnano model 100 particle sampler. During

operation, particles enter the device via the white inlet tube at the top of the sampler.

ESPnano Characterizes Hazardous Airborne Particles in the WorkplacePhoto by NIOSH
For More Information

For more information on the ESPnano particle sampler, contact the NIOSH Mining Program (mining@cdc.gov).

Find NIOSH products and get answers to workplace safety and health questions:

commercialization of the ESPnano, this nanoparticle sampler has 

become an important tool for industrial hygienists and air quality

researchers. This technology fills a unique gap in air quality

monitoring, and its worldwide use is evidenced by many citations

of the original work as well as published references to its application 

for the characterization of hazardous airborne particulate matter 

[Barone et al. 2012; Jung et al. 2013] and in occupational exposure 

studies [Miller et al. 2010b; Bugarski et al. 2016]. This device will be

an important component in future work aimed at methods for

characterizing and assessing nanoaerosols and other airborne

hazards in the workplace.

References

Barone TL, Storey JME, Youngquist AD, Szybist JP [2012]. An analysis of direct-injection spark-ignition 

(DISI) soot morphology. Atmos Environ 49:268–274.

Bugarski AD, Hummer JA, Stachulak JS, Miller AL, Patts LD, Cauda EG [2016].

Emissions from a diesel engine using Fe-based fuel additives and a

sintered metafiltration system. Annals of Occup Hygiene 60(2):252–262.

Jung HS, Miller AL, Park K, Kittelson DB [2013]. Carbon nanotubes among diesel exhaust particles: real 

samples or contaminants? J Air J Air Waste Man Assoc 63(10):1199–1204.

Miller AL, Frey G, King G, Sunderman C [2010a]. A handheld electrostatic precipitator

for sampling airborne particles and nanoparticles. Aerosol Sci and Tech 44(6):417–427.

Miller AL, Drake PL, Hintz P, Habjan M [2010b]. Characterizing exposures to airborne metals and nanoparticle emissions in a refinery. Annals of Occup Hygiene 54(5):504–513.

“sampling keys” onto which various types of sampling 

media can be loaded. To take a sample, the user slides a key 

into the device and selects a sampling time from the menu. 

Sampling time selection is aided by a table (Table 1) on the 

back of the ESPnano and is dependent on airborne particle 

concentration, with approximate number concentrations 

measured in particles per cubic centimeter (cc). When the 

user selects “run” from the menu, the device begins

sampling, and within seconds collects particles as large as 

tens of microns and as small as ten nanometers, providing

representative samples over a wide range of particle sizes. 

The capability of collecting such a wide range of particle

sizes in a very short time makes this device advantageous 

for research purposes or when doing air quality surveys at 

field sites. Such a wide size range is often not possible with 

other techniques, especially ones that are field-portable.

Table 1. Reference sampling time information (approximated)

The operating principle for the ESPnano entails using high 

voltage to generate an intense electrical field in which

particles are charged, causing them to migrate toward a 

negative electrode to which collection media has been

attached (Figure 2). This allows all sizes and types of

particles to be deposited by electrostatic deposition onto a 

variety of different sampling media, which can then be sent 

to a lab for offline analyses by TEM, SEM, and EDS.

Future Use

Since the original 2010 publication describing the

ESP technology and the subsequent licensing and

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Monthly NIOSH eNews: cdc.gov/niosh/eNews

DHHS (NIOSH) Publication No. 2020–111

DOI: https://doi.org/10.26616/NIOSHPUB2020111

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Example Source Approximate Number 

Concentrations

Suggested Cycle Time

Diesel - undiluted 

emissions

108 particles/cc 1 second

Industrial process 

emissions

107 particles/cc 1 second

Factory/

production area

106 particles/cc 2-5 seconds

Warehouse/

shipping dock

105 particles/cc 20-50 seconds

Office air 104 particles/cc 200-500 seconds

Accessible version: https://www.cdc.gov/niosh/mining/content/ESPnano.html

Figure 2: Particles entering the ESPnano inlet pass through a high-voltage 

electrical field inside the device that simultaneously charges and collects 

them onto media that rests on the negative electrode plate.