Filter cassette

Attach the collection device (filter cassette, charcoal tube, etc.) to the shirt collar or as close as practical to the nose and mouth of the employee). Employee exposure is that exposure which would occur if the employee were not using a respirator. The inlet should always be in a downward vertical position to avoid gross contamination. Position the excess tubing so as not to interfere with the work of the employee. 

Closed face sampling Sampling performed through a small hole in the top of a filter cassette. 

The primary sample types used for field spiking were freshly prepared soapy distilled water (soapy water), air filter cassettes set up with 2.0 L/min. of air flow, and foil-backed patches of underwear cloth with a cover flap of coveralls cloth. The spiking solution was applied to the underwear material and the coveralls patch was then folded down to cover the spiked area. The patch was then exposed to air and sunlight for the duration of the trial in an area upwind from the trial site. The washwater samples for spiking consisted of 50-mL samples of soapy water prepared by putting on latex examination gloves and washing with Ivory soap in deionized water prior to the trial in the same way the operator would wash his hands. 

Dust samples were collected by the probe/filter configuration shown in Figure 2. The filter used to trap the explosive dust was a 37mm plastic filter cassette. To monitor the actual flow rate, a rotometer was used. The calculation for each traverse point dust concentration was obtained from... 

Figure 4. Expanded view of standard three-piece filter cassette. (Drawing courtesy of the...

Generally, any of these filters satisfied the requirements for collection of most of the particulates to be analyzed. However, certain analytes and their associated analytical methods gave better results with alternative filters. The filter cassette was also tested as part of the total sampling device. Some substances were partially collected on the cassette, and the substance had to be rinsed from the cassette with solvent to avoid loss. 

C.I. Direct Brown 95 at this new LAQL. Because of the problems encountered with the midget impinger humidification system, changes were made to incorporate one large impinger and supply the humidified air to the filter cassettes at atmospheric and not reduced pressure. Again, 60 L of humidified air were pulled through each cassette. The results of this study are shown in Table V. Recoveries of C.I. Direct Black 38 and C.I. Direct Brown 95 were approximately 90%. 

The sampling operation involves collection of an aerosol sample that is representative of the particle size distribution and concentration of the sampled atmosphere. The efficiency of particle transport and collection operations are dependent on the particle size, sampling velocity, the geometry of the sampling apparatus and the properties of the collection medium. In the present work, a 37 mm diameter membrane filter (0.3 ym pore size) is the primary collection medium under evaluation. The filter is housed in a standard filter cassette and effects of filter-holder inlet geometry are also being investigated. 

The chamber is being used to produce replicate samples of Pb, , and Se at several loading levels for the analytical studies. Filter sampling and collection efficiencies are also being explored using Pb aerosols and by varying the sample flow rate through the 37 mm filter cassettes from 0.1 to 4.0 Lpm. 

Another factor regarding recovery of the sample is that the complete sampling device should be tested, not just the filter itself. Generation of test atmospheres may be necessary to perform these tests. This became most apparent in the work on thiram where the filter cassette top collected thiram to some degree. The amount varied from 1% to 12% of the total sample. Fortunately, the thiram on the cassette was stable so that cassettes containing filter samples could be stoppered and shipped for analysis. In laboratory analysis, a separate, cassette-rinse, was analyzed based on a 5-ml wash of the cassette top with acetonitrile. 

Dusts, silica, metal powder, carbon particles, and particulate matter are collected over membrane filters of appropriate pore size. Filter cassettes are used for this process. A membrane filter having the same diameter as the cassette is placed inside the cassette, one end of which is connected to the sampling pump. A measured volume of air is then sampled. While air can pass through the pores of the filter, the suspended particles get deposited on the filter. 

Figure 2. Personal sampling device consisting of a filter cassette and a 10-mm...

Figure 3. Calibration setup for personal sampling pump with filter cassette...

Light Microscopic Method. Phase contrast microscopy (PCM) accurately assesses fiber exposure levels for fibers 5 pm in length and >0.25 pm in diameter. Furthermore, PCM cannot differentiate between asbestos and nonasbestos fibers. Currently, the standard method for the determination of airborne asbestos particles in the workplace is NIOSH Method 7400, Asbestos by Phase Contrast Microscopy (NIOSH 1994a). OSHA considers that sampling and analytical procedures contained in OSHA Method ID-160 and NIOSH Method 7400 are essential for obtaining adequate employee exposure monitoring. Therefore, all employers who are required to conduct monitoring are required to use these or equivalent methods to collect and analyze samples (OSHA 1994). In NIOSH Method 7400, asbestos is collected on a 25 mm cellulose ester filter (cassette-equipped with a 50 mm electrically-conductive cowl). The filter is treated to make it... 

Particle size selective OEL have already been established to address the problems associated with specific health effects, especially within fields where solid aerosol particles are to be measured. A number of filter cassette designs have been tailored to sample specific size ranges of the total aerosol fraction, in order not to overestimate the exposure causing health effects by inhalation. Since only particles less than approximately 100 /rm can be inhaled and the inhaled aerosol fraction is most certainly the main contributor to specific health effects among workers exposed to isocyanates, it seems reasonable to use sampling devices designed for sampling of the inhalable... 

Fig. 6.69 Total dust sampling heads according to BIA for personal sampling on the left is a GGP system, and on the right a standard total dust sampling head in the background are filter cassettes.

A known volume of air is drawn at 1.51/min through a filter cassette containing a sodium bisulfate-treated glass-fiber filter. A minimum sampling time of 1 h is recommended. The treated filter is transferred to a centrifuge tube and extracted in ethanol/water/sodium hydroxide solution and back-extracted into ammoniated heptane using N-ethylnornicotine as internal standard. An aliquot of the heptane layer is analyzed by gas chromatography with thermionic-specific detection. 

Filters For total particulate/aerosol sampling, the open- or close-faced 37 mm filter cassette is the most popular in many countries. A newer type of sampler for inhalable dust is the lOM sampler with a 25 mm filter. Many studies have shown that the lOM sampler provides the best reference for inhalable aerosol. Other samplers that are emerging for this purpose are Respicon, and the Button samplers. There are several types of filters commonly used for this purpose glass fiber, mixed cellulose ester fiber (MCE), and poly(vinyl chloride) (PVC) filters. They are selected based on their ability to collect material and their suitability for laboratory analysis. For example, PVC filters are normally used for gravimetric analysis and MCEs are used when a chemical analysis is needed followed by digestion or extraction. 

During a change of the pre-filter the operator has to wear a protective P2- or P3 mask (see Sect. 26.4.1) for dust and aerosols. The exhaust unit fan is switched on, so dust particles are trapped in the HEPA or ULPA filter cassette. Clean the filter frames and remove the old filters in a closed bag. 

A special case was concerned with measurement of uranium aerosols generated when DU munitions penetrate armored vehicles (Parkhurst 2003). In this study, DU penetrators were fired at a tank and another armored vehicle and the aerosols were collected by different means (filter cassettes, cascade impactors, five-stage cyclone, and a moving filter). Wipe samples were also collected from surfaces and deposition trays. Analysis included particle size distribution, morphology, uranium oxide phases, and dissolution in vitro. The uranium mass was determined by different methods radioanalytical beta spectrometry for some filters and ICPMS, ICP-AES, and KPA for other samples. 

Immediately before sampling, remove the plastic plugs from the filter cassettes. 

The preferred coiiection device shaii be the 25-mm diameter cassette with an open-faced 50-mm eiectricaiiy conductive extension cowi. The 37-mm cassette may be used if necessary but oniy if written justification for the need to use the 37-mm filter cassette accompanies the sample results in the employee s exposure monitoring record. Do not reuse or reload cassettes for asbestos sample collection. 

Calibrate each personal sampling pump before and after use with a representative filter cassette installed between the pump and the calibration devices. 

Collection Procedure A known volume of air is drawn through a 37-mm diameter filter cassette containing a 0.8-tim mixed cellulose ester membrane filter (MCEF). 

Filter cassette unit for air sampling A 37-mm diameter mixed cellulose ester membrane filter with a pore size of 0.8-nm contained in a 37-mm polystyrene two- or three-piece cassette filter holder (part no. MAWP 037 AO, Millipore Corp., Bedford, MA). The filter is supported with a cellulose backup pad. The cassette is sealed prior to use with a shrinkable gel band. 

A calibrated personal sampling pump whose flow is determined to an accuracy of 5% at the recommended flow rate with the filter cassette unit in line. 

Replace the end plugs into the filter cassettes immediately after sampling. Record the sampling conditions. 

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