control of bioaerosols

Control of Bioaerosols

Concentrations in Air

• Concentrations of indoor bacteria range from <100-1500 cfu/m3; avg 0-500– heated dwellings lower

• Avg concentrations of outdoor bacteria 200-1000

• Avg concentrations of indoor Fungi range from 10-500

• Avg concentrations of Outdoor Fungi range from 100-1000

Air Quality Control Methods

SourceControl

VentilationPressureControl

AirTreatment

Air Filtration

• Part of most HVAC systems• Hospitals have very intricate systems• No universal standard method for evaluating

filter performance– Thus advertised efficiencies may be misleading

• Most difficult range of particles to filter 0.2 to 0.3 micron; generally particles categorized as > 0.5 or < 0.5 microns

• Peak Particle Removal with 12-15 ACH

Types of Filters

• Fiberglass- typical household filter 5-7% effective

• Electronic- lose filtering 50% capacity in first week

• HEPA- High Efficiency Particulate Air, 99.97% of pollutants at 0.3 microns

• ULPA- Ultra Low Penetration Air, 99.9997% of particles as 0.1 micron

• Electrostatic- “static charged”, 95%

Other Air Treatments

• Ionizer- negative ion generation

• Ozone- good disinfectant, safety risk

• UV- good disinfectant, 253.7nm, long exposure times?

Cundith et al.Console filtration

Cundith et al., Meat Processing Plant

• Deployed EP filters with scanning UV

• Three Rooms (100% recirculation)– Processing- 10ºC, 110m3, 3 m/min– Chill Cooler- 0-2ºC, 130m3, 21 m/min– Aging Cooler- 0-2ºC, 360m3, 8m/min

Kujundzic E, et al..•  

Effects of ceiling-mounted HEPA-UV air filters on airborne bacteria concentrations in an indoor therapy pool building. J Air Waste Manag Assoc. 2005 Feb;55(2):210-8.

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The purpose of this study was to assess the effectiveness of a new generation of high-volume, ceiling-mounted high-efficiency particulate air (HEPA)-ultraviolet (UV) air filters (HUVAFs) for their ability to remove or inactivate bacterial aerosol. In an environmentally controlled full-scale laboratory chamber (87 m3), and an indoor therapy pool building, the mitigation ability of air filters was assessed by comparing concentrations of total bacteria, culturable bacteria, and airborne endotoxin with and without the air filters operating under otherwise similar conditions. Controlled chamber tests with pure cultures of aerosolized Mycobacterium parafortuitum cells showed that the HUVAF unit tested provided an equivalent air-exchange rate of 11 hr(-1). Using this equivalent air-exchange rate as a design basis, three HUVAFs were installed in an indoor therapy pool building for bioaerosol mitigation, and their effectiveness was studied over a 2-year period. The HUVAFs reduced concentrations of culturable bacteria by 69 and 80% during monitoring periods executed in respective years. The HUVAFs reduced concentrations of total bacteria by 12 and 76% during the same monitoring period, respectively. Airborne endotoxin concentrations were not affected by the HUVAF operation.

Laboratory Control

• BSCs

• Centrifuge containment

• HVAC

Class I

• Personnel and Environmental Protection

• No Product Protection• Similar to fume hood

with HEPA exhaust• 75 LPM• Hard-ducted to BLDG

exhaust• 0.5 inches water

Class I

• Some have integral blower

• Must be turned off in case of BLDG exhaust failure

• Good design to surround all positive pressure plenums with vacuum

Class IIA/B3 (Now Class II A2)

• 30/70 exhaust/recirculation• HEPA filtered on exhaust

and recirculation• 75 LPM• Hard-ducting not

recommended • Not rated for volatiles or

toxics

Class IIB1• Originated with NCI designed

cabinet• 70/30 exhaust/recirculation• HEPA filtered on exhaust,

recirculation and inflow• Personnel, environment and

product protection• 100 LPM• 70% downflow through rear grill;

30% front grill• Hard-ducted; preferably

dedicated

Class IIB2

• Total exhaust • Personnel, environment and

product protection• HEPA filtered on inflow and

exhaust• 100 LPM• Hard-ducted;1.5 inches

water; must be interlocked; ideally dedicated

• With internal blower may not be hard-ducted

Class III

• Designed for work with BSL 4 agents• Interchange box• Heavy duty rubber gloves• HEPA filtered on supply and exhaust (double or

incinerator)• Hard-ducted; dedicated exhaust 0.5 inches water

BAG-IN BAG-OUT (BIBO)

• Additional layer of protection

• Between BSC and BLDG exhaust

• HEPA• Required for BSL3/BSL4

laboratories

Respirators/PAPRs

Fit TestingBefore an employee uses any respirator with a negative or positive pressure tight-fitting facepiece, the employee must be fit tested with the same make, model, style, and size of respirator that will be used.

Qualitative Fit Test (QLFT)

A pass/fail fit test to assess the adequacy of respirator fit that relies on the individual’s response to the test agent.

Quantitative Fit Test (QNFT)An assessment of the adequacy of respirator fit by numerically measuring the amount of leakage into the respirator.