Use of Portable HEPA Filtered Ventilation Units. HEPA Filtered Ventilation Used to “capture”...

Use of Portable HEPA Use of Portable HEPA Filtered Ventilation UnitsFiltered Ventilation Units

HEPA Filtered VentilationHEPA Filtered Ventilation

Used to “capture” airborne Used to “capture” airborne particulate and confine its spreadparticulate and confine its spread

Workers need to understand the Workers need to understand the dynamics of how to capture dynamics of how to capture particulate to be effective.particulate to be effective.

REQUIREMENTSREQUIREMENTS

Portable air-handling equipment used Portable air-handling equipment used in CAs, HCAs, or ARAs should be in CAs, HCAs, or ARAs should be equipped with HEPA filtersequipped with HEPA filters

HEPA filters should meet the HEPA filters should meet the efficiency and construction efficiency and construction requirements for HEPA filtersrequirements for HEPA filters


Maximum flow rate of the device Maximum flow rate of the device should not exceed the flow rate the should not exceed the flow rate the HEPA filter was testedHEPA filter was tested

Units should be aerosol tested before Units should be aerosol tested before initial use, annually, and when initial use, annually, and when opened. opened.


Uniquely marked and labeledUniquely marked and labeled

Controlled by RWPControlled by RWP

Controlled to prevent Unauthorized Controlled to prevent Unauthorized UseUse


Designed to ensure HEPA filter Designed to ensure HEPA filter integrity under conditions of use, andintegrity under conditions of use, and

Designed to prevent unauthorized or Designed to prevent unauthorized or accidental access to inner surfacesaccidental access to inner surfaces

Characteristics of Portable Characteristics of Portable Vent SystemVent System

Need “Nuclear grade” equipmentNeed “Nuclear grade” equipment Keep hose/duct length short with Keep hose/duct length short with

minimum bends. Route through low minimum bends. Route through low traffic areas.traffic areas.

Bends should have minimum bend radius Bends should have minimum bend radius of 2-2.5 times hose/duct diameter. Sharp of 2-2.5 times hose/duct diameter. Sharp bends are equivalent to adding more bends are equivalent to adding more hose or duct equal to 6-8 times hose hose or duct equal to 6-8 times hose diameter.diameter.


Install straight duct section of a least 6 Install straight duct section of a least 6 equivalent duct diameters at a location equivalent duct diameters at a location where hose connects to fan housingwhere hose connects to fan housing

Hose/duct should be round, smooth-Hose/duct should be round, smooth-bore and free of obstructionsbore and free of obstructions

If dampers must be used, install If dampers must be used, install midway in hose and secure with midway in hose and secure with tamper-proof devicetamper-proof device


Use “localized” or “capture” ventilation Use “localized” or “capture” ventilation close to contamination sourceclose to contamination source

Flow rate must be high enough to Flow rate must be high enough to capture particulate and keep it in air capture particulate and keep it in air streamstream

Position hose within one duct-Position hose within one duct-diameter and modify the suction to diameter and modify the suction to pull air from the region where airborne pull air from the region where airborne particulate is being producedparticulate is being produced

% of Diameter

100%

60%

30%

15%

7.5%

Flow Contours

% of VelocityVelocity Contours

• Circular hose inlet opening

• % of opening velocity

Capture VelocityCapture Velocity

The air velocity at any point in front The air velocity at any point in front of a hood or hose/duct opening of a hood or hose/duct opening necessary to overcome opposing air necessary to overcome opposing air currents and capture the currents and capture the contaminated particles at that point contaminated particles at that point and cause them to flow into the and cause them to flow into the ventilation system.ventilation system.

Capture VelocityCapture Velocity

Recommend minimum of 125-200 Recommend minimum of 125-200 fpm at contamination sourcefpm at contamination source

In quiet air need 50-100 fpmIn quiet air need 50-100 fpm

During grinding, need 500-2000 fpm During grinding, need 500-2000 fpm to capture high velocity particles to capture high velocity particles

Face VelocityFace Velocity

Air velocity in feet per minute (fpm) Air velocity in feet per minute (fpm) at hood, hose or duct opening.at hood, hose or duct opening.

This velocity varies based on the size This velocity varies based on the size of the system, amount of hose or of the system, amount of hose or ducting, fittings, and other system ducting, fittings, and other system losses due to the configuration. losses due to the configuration.

Minimum Duct VelocityMinimum Duct Velocity

Minimum air velocity required to move Minimum air velocity required to move particulates in the air stream.particulates in the air stream.

Normally, this ranges from Normally, this ranges from 1500-4500 1500-4500 fpmfpm

This velocity depends on type and size This velocity depends on type and size of material, i.e., vapor, gas, fume, of material, i.e., vapor, gas, fume, dust, debris, etc. dust, debris, etc.

Characteristics of Portable Characteristics of Portable HEPA Vent SystemHEPA Vent System

Use funnel, scoop, or hood to improve Use funnel, scoop, or hood to improve capturecapture

Force incoming air to pass through Force incoming air to pass through region that contains airborne region that contains airborne particulateparticulate

Place vent suction at 90 to 180 Place vent suction at 90 to 180 degrees from worker on opposite side degrees from worker on opposite side of source at one duct diameter or lessof source at one duct diameter or less

Characteristics of Portable Characteristics of Portable HEPA Vent SystemHEPA Vent System

System fitting should be tapered to System fitting should be tapered to reduce restrictions. Most units are reduce restrictions. Most units are not tapered to cut cost and save not tapered to cut cost and save space.space.

Securely seal joints to avoid leaks Securely seal joints to avoid leaks and increase flowand increase flow

Install demister when needed to Install demister when needed to remove liquid from damp air. Damp remove liquid from damp air. Damp HEPA filters lose tensile strength.HEPA filters lose tensile strength.

Characteristics of Portable Characteristics of Portable HEPA Vent System HEPA Vent System

Locate system in a well-lighted and Locate system in a well-lighted and weather protected areaweather protected area

Ensure air discharged by the system Ensure air discharged by the system does not disturb contamination or does not disturb contamination or insulation. insulation.

If used for “hot work” use metal If used for “hot work” use metal ducting and spark arrestor to remove ducting and spark arrestor to remove sparks and prevent firesparks and prevent fire

Air Flow CalculationsAir Flow Calculations

Air changes in the tent work section Air changes in the tent work section should provide a minimum of 7-12 air should provide a minimum of 7-12 air changes per hour or whatever the facility changes per hour or whatever the facility requires. Many facilities use 20 air requires. Many facilities use 20 air changes per hour as the desired flow. changes per hour as the desired flow.

Air changes are determined by dividing Air changes are determined by dividing the rated CFM of the vent system into the the rated CFM of the vent system into the volume of the containmentvolume of the containment

Air Flow CalculationsAir Flow Calculations

For Example: For Example: Tent is 10’ x 12’ x 8 = 960 ft3Tent is 10’ x 12’ x 8 = 960 ft3 Vent system is rated at 300 CFMVent system is rated at 300 CFM

960 ft3960 ft3 x x 60 min60 min = 18.75 AC/hr = 18.75 AC/hr 300 CFM 1 hr300 CFM 1 hr

Air FlowAir Flow

If localized or capture ventilation is If localized or capture ventilation is used, the important thing to consider used, the important thing to consider is the is the amountamount and and directiondirection of flow at of flow at the contamination source and the the contamination source and the worker’s breathing zone. worker’s breathing zone.

In SummaryIn Summary

Get the hose/duct close, within one Get the hose/duct close, within one duct diameterduct diameter

Install scoop, hood, or flange to force Install scoop, hood, or flange to force incoming air to pass through the incoming air to pass through the contamination sourcecontamination source

Smoke test prior to work and look at Smoke test prior to work and look at worker’s body positionworker’s body position

Check blower dischargeCheck blower discharge

Vent & BalanceVent & Balance

When system is set up, call Vent & When system is set up, call Vent & Balance at 373-2746 or 373-9275 to Balance at 373-2746 or 373-9275 to arrange for aerosol testingarrange for aerosol testing

Resources You NeedResources You Need

Industrial Ventilation ManualIndustrial Ventilation Manual - Purchase from American Conference - Purchase from American Conference

of Governmental Hygienists at (513) of Governmental Hygienists at (513) 742-2020 or Website 742-2020 or Website http://www.acgih.org/store/. Cost is http://www.acgih.org/store/. Cost is about $100.00 and they take a P-about $100.00 and they take a P-Card. They also sell another book on Card. They also sell another book on “Ventilation for Contaminant Control”.“Ventilation for Contaminant Control”.

Use of HEPA Filtered Use of HEPA Filtered Vacuum Cleaners Vacuum Cleaners

CAUTIONCAUTION

Improper use of vacuum cleaners Improper use of vacuum cleaners may result in the generation or may result in the generation or airborne radioactivity, loose surface airborne radioactivity, loose surface contamination, or high dose ratescontamination, or high dose rates

Requirements for Using Requirements for Using Vacuums for Rad WorkVacuums for Rad Work

Should be equipped with HEPA filters that meet Should be equipped with HEPA filters that meet special efficiency and construction special efficiency and construction requirements requirements

Nuclear Safety Review should be performed & Nuclear Safety Review should be performed & documented before use with fissile materialdocumented before use with fissile material

The maximum flow rate of the vacuum should The maximum flow rate of the vacuum should not exceed the flow rate used to test the HEPA not exceed the flow rate used to test the HEPA filter filter

HEPA Filtered VacuumsHEPA Filtered Vacuums

HEPA filters remove debris from the air HEPA filters remove debris from the air stream, including radioactive particlesstream, including radioactive particles

Vacuum cleaners collect most of the Vacuum cleaners collect most of the debris before it reaches the filter in debris before it reaches the filter in disposable bags or containersdisposable bags or containers

Some are designed for collecting wet Some are designed for collecting wet materials and some are explosion-proofmaterials and some are explosion-proof


Leak test prior to use, annually, and Leak test prior to use, annually, and when opened*. Also when dropped, when opened*. Also when dropped, jarred, or exposed to water vapors, jarred, or exposed to water vapors, chemicals, or high temperatures.chemicals, or high temperatures.

* If the vacuum is designed to be * If the vacuum is designed to be serviced without effecting the HEPA serviced without effecting the HEPA filter seal, it does not require filter seal, it does not require retesting.retesting.


Vacuum cleaners should be:Vacuum cleaners should be:

1. Uniquely marked and labeled1. Uniquely marked and labeled

2. Controlled by an RWP,2. Controlled by an RWP,

3. Controlled to prevent unauthorized 3. Controlled to prevent unauthorized use,use,


4. Designed to ensure HEPA filter 4. Designed to ensure HEPA filter integrity under conditions of use, andintegrity under conditions of use, and

5. Designed to prevent unauthorized 5. Designed to prevent unauthorized or accidental access to the inner or accidental access to the inner surfaces of the vacuum cleanersurfaces of the vacuum cleaner


Radiation and contamination surveys Radiation and contamination surveys should be performed periodically should be performed periodically while in use and labels updated. while in use and labels updated.

The frequency of radiation surveys The frequency of radiation surveys should depend on the specific use of should depend on the specific use of the vacuum the vacuum

Air samples should be taken if the unit Air samples should be taken if the unit is used in a High Contamination Areais used in a High Contamination Area


Surveys should be performed before, during Surveys should be performed before, during and at the completion of work that has the and at the completion of work that has the potential for causing changes in levels of potential for causing changes in levels of radiation and radioactivity. Recommend radiation and radioactivity. Recommend marking survey points on the vacuum cleanermarking survey points on the vacuum cleaner

Survey frequencies should be based on Survey frequencies should be based on potential conditions, probability of change potential conditions, probability of change and area occupancy factors.and area occupancy factors.

GuidelinesGuidelines

Contact line organization for vacuumContact line organization for vacuum

Verify unit has been tested within last year Verify unit has been tested within last year (365 days)(365 days)

Ensure any security seals are intactEnsure any security seals are intact

Inspect hoses and vacuum for integrityInspect hoses and vacuum for integrity


If vacuum is contaminated, check If vacuum is contaminated, check bagging on hose end and labelsbagging on hose end and labels

Position vacuum close to work and Position vacuum close to work and route hose through low traffic areasroute hose through low traffic areas

Keep hose straight with gradual bendsKeep hose straight with gradual bends


Securely clamp or tape hose Securely clamp or tape hose connectionsconnections

Secure vacuum in upright positionSecure vacuum in upright position

If wet/dry unit is used, verify any If wet/dry unit is used, verify any drain valves are shut drain valves are shut


If used for ventilation, position hose If used for ventilation, position hose within one duct diameter so airborne within one duct diameter so airborne particles are drawn away from particles are drawn away from worker. On shrouded tooling, the worker. On shrouded tooling, the hose is connected to the toolhose is connected to the tool

If used to remove debris, don’t If used to remove debris, don’t vacuum large particles or materials vacuum large particles or materials that will plug the hose. that will plug the hose.


Consider installing collector to Consider installing collector to remove highly radioactive debris remove highly radioactive debris before it reaches the vacuumbefore it reaches the vacuum

In addition, a filter could be installed In addition, a filter could be installed in the vacuum cleaner hose so the in the vacuum cleaner hose so the HEPA filter in the vacuum cleaner HEPA filter in the vacuum cleaner stays low rad.stays low rad.


If collecting liquids or damp debris If collecting liquids or damp debris ensure vacuum cleaner is a wet/dry ensure vacuum cleaner is a wet/dry unitunit

Ensure procedures are established so Ensure procedures are established so the unit is not overfilled and the the unit is not overfilled and the workers understand how the unit will workers understand how the unit will be used and emptiedbe used and emptied


If used to collect low-level rad waste, If used to collect low-level rad waste, don’t mix with “TRU” or “Mixed don’t mix with “TRU” or “Mixed Waste”Waste”

If Vent & Balance sticker is torn or If Vent & Balance sticker is torn or integrity seals are broken, the unit integrity seals are broken, the unit must be removed from service and must be removed from service and retested prior to useretested prior to use

PrecautionsPrecautions

Don’t run electrical vacuums for long Don’t run electrical vacuums for long periods or they may overheat and periods or they may overheat and catch firecatch fire

Don’t use an electric vacuum cleaner Don’t use an electric vacuum cleaner to remove explosive gases. Use an to remove explosive gases. Use an explosion-proof unit and get approval explosion-proof unit and get approval from safetyfrom safety

Use of Portable HEPA Filtered Ventilation Units. HEPA Filtered Ventilation Used to “capture”...

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