Separating the In from the Out

The process starts with collection of accurate data detailing the levels of airborne particulates. One tool that has proven highly useful is the hand-held laser particle counter..

A particle counter operates by pumping an air sample of known volume-generally one liter-past a laser beam. As dust particles in the air stream pass through the beam, each one reflects or “scatters” the laser light. A photodetector senses the scattered light and generates an analog electrical signal. Larger particles scatter more light and create higher-voltage electronic “hits.” Onboard electronics track the hits and count the particles in six size categories, ranging from .3 µm to 10 µm. Particles larger than 10 µm generally settle out of the air.

Particle counters can take new counts as often as needed, from every second up to once a day, and store 5000 records of date, time, counts, relative humidity, temperature, sample volumes, alarms and location label records in its onboard memory. Stored readings may then be downloaded to a personal computer. As an alternative, the particle counter can be connected directly to a PC for real time downloads.

The accuracy, speed and compact size some particle counters make them useful for baseline particulate testing, problem detection and remediation and system maintenance.

• Baseline Testing: This determines where particles come from and what they are. How does the HVAC system perform in controlling contaminants from inside or outside of the facility? It is a good practice to test particulate levels both inside and outside. Ideally, inside air will be cleaner and contain fewer particulates than outside air. In addition, plant operators must determine the source of indoor particulates. Do particles come from outside, from plant operations, from the building interior, equipment or occupants, or from a contaminated HVAC system?

  In addition to identifying the number and source of particles, it is important to know what the particles consist of. Using a portable sampling device, airborne contaminants are captured on a biological medium (a petri dish or agar strip), then analyzed for type, frequency and size. Cultures can be grown and analyzed in the laboratory to determine what kinds of bacteria, molds or yeast are present, what particle size each is associated with, and what health problems they may pose.

• Tracking Down Contaminant Sources: A hand-held counter is easily moved around the facility to quickly test particle levels and identify problems at multiple locations. If levels are higher by the loading dock, loading procedures should be refined-for instance, reducing truck idling time or minimizing the time doors are open. If specific machines or operations produce high levels of particles, dust collectors or modified processes may cure the problem. If particle levels are high where HVAC systems supply conditioned air, air ducts or cooling coils may need cleaning, or filters may need maintenance.
• Maintenance Testing: This is done periodically to check particle levels, identify any emerging problems and verify that remedial measures remain effective. An increased particle count could show that the HVAC ducts have developed a leak, filters need renewal or staff members have strayed from standard operating procedures. Higher counts could even indicate that mold or bacteria are growing inside the HVAC system.

If baseline testing has shown that a specific pathogen is associated with a specific size of particle, an increase in that particle size could provide early warning that the organism is reproducing. Verification would require sampling and lab analysis.

In conclusion, airborne contaminants pose significant risks to food producers. Productivity, profitability and reputation all could be harmed by an incident of airborne food contamination, especially a food recall. Laser particle counters provide plant operators a convenient, low cost tool to monitor air quality, identify sources of airborne particulates and provide early warning regarding the emergence of contaminant sources. Given early warning, managers can resolve underlying problems and reduce the company’s risk and liability.