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Inline HEPA Filter on CNT Glove Weighing 

Process Exhaust Duct Airborne Testing Report

 

Executive Summary:

On December 2, 2010 “NIOSH Current Intelligence Bulletin: Occupational Exposure to 

Carbon Nanotube and Nanofibers” was published by the National Institute for 

Occupational Safety and Health. 

Based upon the data from animal studies, a recommended exposure limit (REL) of 

1.0ug/m3 has been established to protect workers’ health. NIOSH came up with this 

REL and calculation based on the animal dose-response date of early-stage fibrotic and 

inflammatory lung response to CNT exposure. This data gives us an estimation of the 

exposure that employees could possibly be exposed to through out their life time. 

Working lifetime exposure concentrations have been calculated based on estimates of 

either the deposited or retained alveolar lung dose of CNT. It goes by an 8-hour timeweighted average (TWA) work shift exposure during a 40-hour work week, 50 weeks per 

year, for 45 years. 

 conducted two samples by using NIOSH Method 7402. This method 

utilizes a Transmission Electron Microscopy (TEM) follow up to a Phase Contrast 

Microscopy (PCM) analysis via NIOSH 7400. Taking advantage of the TEM's ability to 

positively identify each fiber(or carbon nanotube), the method determines the percentage 

of asbestos fibers (or carbon nanotubes) versus non-asbestos fibers in the sample. This 

method helps determine the potential exposure for all workers who could be exposed to 

CNTs. This test was done by using a SKC Leland Legacy air pump. It is connected 

1⁄4’’ of tygon r-3603 tubing  Preloaded Quartz Fiber Cassette, MCE backing, 0.8um, 

37mm connected to another 1⁄4’’ tygon r-3603 tubing. Then we will send this sample to 

Ph.D. Senior Research 

Scientist) for analysis via NIOSH Method 7402 for asbestos fibers testing. 

Process Description: 

Our Hypothesis: The purpose of this experiment to determine the effectiveness of the 

inline 0.5um HEPA filter and its ability to remove CNTs. Our expectations prior to 

performing testing was to have CNTs being detected on the “Pre-HEPA Filter” sample 

and not on the “Post-HEPA Filter” sample
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Sample 17: 

On May 29, 2013 we began our process by calibrating our SKC Leland Legacy Pump. 

Calibration Flo w Average Date of 

Calibration 

Process 

Descriptions 

At -40 L/min (this is the amount of 

flow that we adjusted so we can get 

the volume of 5L/min At -40 L/min 4.9782 4.9782 5/29/2013 

SKC Leland 

Legacy Pump 

was connected 

to Bios 

Defender 510 

calibration 

machine 

 4.8657 4.9219 

 5.0654 5.0654 

 4.964 5.0147 

 4.9059 4.9059 

 5.0152 4.9605 

 

Then we adjusted back up to 5L/min 

so we can compare the flow volume 

with the Bios Defender Calibration 

MachinAt 5L/min 5.0256 4.9782 5/29/2013 

SKC Leland 

Legacy Pump 

was connected 

to Bios 

Defender 510 

calibration 

machine 

 5.0019 5.0019 

 4.8823 4.8823 

 4.9827 4.9209 

 4.9478 4.9388 

 5.0311 4.9426 

On the same day at the facility at 10:54 AM we performed an 

airborne sampling test on the exhaust duct (Pre-Hepa Filter). We drilled a 1⁄4” hole into 

the Glove Box exhaust duct pre the inline HEPA filter and then we inserted the1/4’’ piece 

of Tygon r-3603 tubing approximately one inch into the hole. Then we connected this to 

the SKC Leland Legacy pump. The Leland Legacy pump was run at 5.00 L/Min for 

420min for a total volume of air of 5.00L/Min x 420min = 2100L. During the run time, 

we had someone in the lab weighing our 3 separate 50grams aliquots of CNTs. This was 

done from 11:30AM to Noon (30 minutes). Samples were sent to 

Ph.D.) for analysis via NIOSH Method 7402 for TEM 

asbestos fibers test. 
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Firgure 1-1 Glove Box Exhaust Duct (Pre-Hepa Filter)
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Sample #18: 

On May 31, 2013 we began our process by calibrating our SKC Leland Legacy Pump. 

Calibration Flo w Average Date of 

Calibration Process Descriptions 

At -40 L/min (this is the 

amount of flow that we 

adjusted so we can get the 

volume of 5L/min 5.0088 5.0088 5/31/2013 

SKC Leland Legacy 

Pump was connected to 

Bios Defender 510 

calibration machine 

 4.9274 4.9274 

 4.9051 4.9051 

 4.9071 4.9071 

 4.9059 4.9059 

 5.0226 5.0226 

 

 

Then we adjusted back up to 

5L/min so we can compare 

the flow volume with the Bios 

Defender Calibration Machine 5/31/2013 

SKC Leland Legacy 

Pump was connected to 

Bios Defender 510 

calibration machine 

 5.0019 5.0019 

 4.8823 4.8823 

 4.9827 4.9209 

 4.9478 4.9388 

 5.0311 4.9426 

 5.0983 5.0983 

On the sa me day at th e facility at 8:54 AM we perfor med an 

airborne sampling test on the exhaust duct (Post-Hepa F ilter). We drilled a 1⁄4” hole into 

the Glove Box exhaust duct pos t the inline H EPA f ilter a nd then we inser ted the 1/4’’ 

piece of Tygon r-3603 tubing appro ximately one inch into the hole. Th en we connected 

this to the SKC Leland Legacy pump. The Leland Legacy pum p was run at 5.00 L/Min 

for 420min for a total volum e of air of 5.00L/ Min x 420min = 2100L. During the run 

time, we ha d som eone in the lab weighing ou r 3 separate 50gram s aliquots of CNTs. 

This was done from 11:30AM to Noon (30 minutes). Sa mples were sent to 

Ph.D.) for analysis via NIOSH Method 7402 

for TEM asbestos fibers test. 

 
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Firgure 1-2 Glove Box Exhaust Duct (Post Hepa Filter)
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Results: 

Two samples were analyzed using NIOSH Method 7402 for TEM asbestos fibers at the 

 Ph.D.. Analysis for both samples 

came back on 6/12/2013 with the results being (ND) Non-Detectable (See Table 1) 

Table 1: NIOSH Method 7402 Airborne Results

Conclusions: 

Based on the results, we concluded that our Glove Box weighing process is not 

introducing enough CNT material into the exhaust duct for it to be detectable. This is 

probably due to our purge and wipe down method while using the Glove Box, which 

significantly reduces or eliminates airborne CNTs from escaping the Glove Box. 

Furthermore, this does not determine what the efficiency of the 0.5um inline HEPA filter 

is for removing CNTs from the exhaust air stream. One could conclude based upon these 

results that the need for this inline HEPA filter could be eliminated as no CNTs were 

found in either sample (pre and post HEPA filter). 

Sample 

# 

Sample 

Description 

Date 

Sample 

Taken 

Type of 

Filter 

Total Air 

Flow 

(L/min) 

Date of 

Results 

EC 

(ug/sq 

cm) 

17 Glove Box Pre 

Hepa Filter 

5/29/2013 Preloaded 

Cassette, 

MCE, 

0.8um, 

37mm, 3 

Piece, PreBanded 

2100 6/12/2013 N/D 

18 Glove Box Post 

Hepa Filter 

5/31/2013 Preloaded 

Cassette, 

MCE, 

0.8um, 

37mm, 3 

Piece, PreBanded 

2100 6/12/2013 N/D