Effectiveness of Dust Control Systems Tested for use During

Masonry Restoration – The Sequel

Michael R. Cooper, CIH, CSP, MPHmichaelcoopermph@gmail.com

RT 232 - Implementing Engineering Controls in Construction - Needs, Challenges, and

EffectivenessJune 4th, 2014

The local exhaust ventilation system evaluations being described are part of a four-year NIOSH-funded project to reduce exposures in construction

To reduce silica exposures during tuckpointing, LEV systems must be:

Commercially available

Capable of capturing airborne dust

Used correctly

Our partnership identified tuckpointing LEV systems to evaluate

Partnership

Contractors

Government

UnionsResearchers

Equipment Manufacturers

The partnership rated the following as the most important criteria when selecting systems for further evaluation:1. Impact on productivity2. Durability3. User acceptance/compatibility with existing

work practices4. Blade visibility

While considering these criteria, the partnership selected tuckpointing LEV systems for further evaluation

1. Impact on productivity2. Durability3. User acceptance/compatibility with existing

work practices4. Blade visibility

The partnership selected from the grinders identified as most prominent in construction

Hilti

Bosch

Metabo

Makita

Dewalt

Arbortech AS170 Brick and Mortar Saw

The partnership selected from seven tuckpointing shroudsICS Dust Director

Hilti Tuck Point Dust Removal Hood

Dustless Technologies CutBuddie II

Bosch Tuckpointing Shroud

Joe Due Blades and Equipment Dust Mizer

Danish Tool North America Tuckpointing Router Bit and Shroud

The partnership selected from 14 vacuums

ICS Vacuums (4 models)

Hilti VC 40U Vacuum

Dustless Technologies HEPA Vac

Bosch Airsweep™ 13 Gallon Wet/Dry Vacuum Cleaner with Power Broker

Little Red Ruwac WNS 2220

Dustcontrol Vacuums (3 models)

Ermator Vacuums (2 models)

Tiger-Vac AS-400 HEPA

Four high ranking systems were tested, with and without LEV, in a controlled setting 1. Metabo grinder, ICS Dust Director shroud with

Dustcontrol 2900 vacuum2. Bosch grinder, ICS Dust Director shroud with

Dustcontrol 2900 vacuum3. Bosch grinders, ICS Dust Director shroud with

Ermator S26 vacuum4. Hilti grinder, Hilti shroud with Hilti vacuum

Test conditions and data collected were consistent between evaluations• Used type S mortar after 28+ days curing• Used filter (HEPA or 99.9%) recommended by

manufacturer• Conducted at least five trials per tool/control

combination• Randomized trial order to minimize bias• Sampled for 16 to 26-minute with LEV, approximately

half as long without LEV• Sampled respirable silica sampling with BGI GK2.69

cyclone at 4.2 lpm• Measured static pressure to monitor flow rate• Documented mass of dust collected by LEV• Documented linear feet of joints cut per minute

Using the Metabo grinder with the Dust Director shroud and DustControl vacuum reduced respirable silica exposures by 95.6%

With LEV Without LEV NIOSH RELLinear (NIOSH REL)Re

spira

ble

Silic

a (m

g/m

3)Using this LEV system reduced exposures by 95.6%

6.3

0.28

0.05

130 times REL

5.5 times REL

Using the Bosch grinder with the Dust Director shroud and DustControl vacuum reduced respirable silica exposures by 98.7%

With LEV Without LEVResp

irabl

e Si

lica

(mg/

m3)

Using this LEV system reduced respirable silica exposures by 98.7%

With LEV Without LEV

Resp

irabl

e Si

lica

(mg/

m3)

0.05

1.8 times REL

140 times REL

0.09

7.2

Using the Bosch grinder with the Dust Director shroud and Ermator vacuum reduced respirable silica exposures by 97.6%

The Ermator S26 is rated to provide sufficient air flow to support two grinders

With LEV Without LEVResp

irabl

e Si

lica

(mg/

m3)

Using this LEV system reduced respirable silica exposures by 98.7%

0.05

16 times REL

690 times REL

0.82

35

Using the complete Hilti tuckpointing LEV system reduced respirable silica exposures by 96.6%

Using this LEV system reduced exposures by 96.6%

With LEV Without LEVResp

irabl

e Si

lica

(mg/

m3)

11

0.38

0.05

7.5 times REL

220 times REL

In addition, we performed limited evaluations with a new grinder shroud from Ermator

Test conditions and data collected were consistent between evaluations• Used type S mortar after 28+ days curing• Used HEPA filter as recommended by

manufacturer• Conducted at least three trials per tool/control

combination• Randomized trial order to minimize bias• Sampled for 24 minutes with LEV and 10 minutes

without LEV• Sampled respirable silica sampling with BGI

GK2.69 cyclone at 4.2 lpm• Measured static pressure to monitor flow rate• Documented mass of dust collected by LEV

Using the Bosch grinder with the Ermator shroud and Ermator S13 vacuum reduced respirable silica exposures by 96.1%

Using this LEV system reduced exposures by 96.1%

With LEV Without LEVResp

irabl

e Si

lica

(mg/

m3)

4.6 times REL

120 times REL5.9

0.23

0.05

Using Bosch grinders with the Ermator shrouds and Ermator S26 vacuum reduced respirable silica exposures by 97.8%

Using this LEV system reduced exposures by 97.8%

With LEV Without LEVResp

irabl

e Si

lica

(mg/

m3) 8.1

0.18

0.05

160 times REL

3.6 times REL

The highest flow rates at the tool were 79 percent of the manufacturers’ specifications for the vacuums tested

The average flow rates after use were 68 to 75 percent of our desired flow rate

The average flow rates returned to 85 to 102 percent of our desired flow rate after filter cleaning

The available tuckpointing LEV systems can be effective but there are challenges

Acceptance and effectiveness varies with the user

Moving the grinder toward the point of dust capture is required

Dus

t Cap

ture

Blade visibility and ability to cut both directions is important

Dus

t Cap

ture

Air flow rate at the tool must be maintained

Average exposure reduction was 97 percent but additional controls may be needed

0 1 2 3 4 5 6 7 8

0.0

0.1

1.0

10.0

100.0

Resp

irabl

e Si

lica

(mg/

m3 )

NIOSH REL

10 X NIOSH REL

Questions?

Michael R. Cooper, CIH, CSP, MPH michaelcoopermph@gmail.com