# Cellulose Insulation (7404)

​CELLULOSE INSULATION MW: 00.00
(C6 H10 O5 )n
METHOD: 7404, Issue 1
7404
CAS: 9004-34-6
RTECS: FJ5691460
EVALUATION: PARTIAL
Issue 1: 15 March 2003
PROPERTIES: solid
SYNONYMS: cellulosic fiber loose fill thermal insulation. Cocoon. SAMPLING
MEASUREMENT TECHNIQUE:
MICROSCOPY, SCANNING ELECTRON (SEM)
ANALYTE:
Fibers, (manual count)
SAMPLER:
FILTER (0.45- to 1.2-um polycarbonate membrane, 25-mm; conductive cowl on cassette)
FLOW RATE:
1 L/min
VOL-MIN: -MAX:
N/A
SAMPLE PREPARATION:
SHIPMENT:
Routine (pack to reduce shock)
EQUIPMENT:
Scanning electron microscope
SAMPLE STABILITY:
CALIBRATION:
SEM performance standard
Stable RANGE:
Not determined
BLANKS:
2 or 10% field blanks per set ACCURACY
RANGE STUDIED:
Not determined
BIAS:
Not determined
OVERALL PRECISION:
Not determined
ACCURACY:
Not determined
Colloidal graphite paint/carbon disk planchet.
ESTIMATED LOD: 1 confirmed cellulose fiber above 95% of expected mean blank value PRECISION:
Not determined
APPLICABILITY: This method is useful for the quantitative determination of airborne cellulose fibers during isulation installation [1].
INTERFERENCES: Non-fibrous cellulose. Very large cellulose fibers and cellulose fibers with convoluted shapes might interfere with fibers characterization. Other fiber types are typically rare and then only in trace amounts.
OTHER METHODS: The counting rules in this method were derived from Method 7400.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​CEL LULO SE INS ULA TIO N: ME TH OD 7404, Issue 1, dated 1 5 Ma rch 2003 - page 2 of 6 EQUIPMENT:
REAG ENT S: 1. Colloidal Graphite.*
1. Sam pler: field monitor, 25-mm , three- piece cassette with ca. 50-m m electrically conductive exten sion cow l and polycarbonate filter, 0.45- to 1.2-um pore size, and backup pad. NOT E 1: Analyze representative filters for fiber b ack grou nd b efore us e. This is needed when field blanks contain fibers. NOT E 2: The electrically conductive extension cowl reduces electrostatic effects. Ground the cowl when possible during sampling. 2. Personal sampling pump, battery or linepowered vacuum, of sufficient capacity to m eet flow rate requireme nts (see step 4), with flexible connecting tubing. 3. Microscope, scanning electron, operated at 15Kv with viewing screen having an inscribed or overlain calibrated scale. 4. Tap e, shrink- or adhes ive-. 5. Tweezers. 6. 25-mm carbon disk planchets. 7. Co lloidal graphite p aint. 8. Grounding wire, 22-gauge, multi strand. 9. Sputter coater.
SPECIAL PRECAUTIONS: Colloidal graphite contains isopropanol, which is flamm able. Take precautions not to ignite it. Use only in well ventilated area. SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Fasten the (uncapped) open-face cassette to the worker’s lapel. The open fac e should be oriented downward. W rap joint between extender and m onitor bod y with tape to keep the joint clean and prevent contamination when disassembled. W here possible, especially at low %RH, attach sampler to electrical ground to reduce electrostatic effects during sampling. 3. Su bm it at least 2 field blanks (or 10% of total samples, whichever is greater) for each set of samples. Rem ove top covers from field blank cassettes and store top covers and cas settes in a c lean area (e.g., a closed bag or box) during sampling. Replace top covers when sampling is completed. 4. Sam ple at 1L/min. NOTE: If the cellulose insulation is being applied dry, sam ple for a shorter period time than if the application is wet. Obtain two personal samples per worker. Sample at same flow rate but for different dura tions. A m inim um dura tion of 1 m inute is app ropriate for very dusty environments. The longer du ration should be dete rm ined by the overall dustiness, size of the area being insulated a nd o ther fa ctors as w ell. 5. At the end of sampling, replace top cover and end plugs. 6. Ship samples with conductive cowl attached in a rigid containe r with pack ing m aterial to m inim ize jostling or da m age . NOTE: Do not use untreated polystyrene foam in the shipping container because electrotatic forces may cause fiber loss from sam ple filter.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​CEL LULO SE INS ULA TIO N: ME TH OD 7404, Issue 1, dated 1 5 Ma rch 2003 - page 3 of 6 SAMPLE PREPARATION: 7. Mount the entire 25-mm filter directly on a carbon disk planchet by painting the planc het w ith a colloidal grap hite paint and im m ediate ly laying the filter, glossy(sam ple) side up, on the planchet. The sam ple num ber is scratched into the back of the planchet prior to mou nting the filter. 8. The planchet is th en placed in a labeled petri dish and perm itted to dry com pletely. 9. W hen dry, place sa m ple in a spu tter co ater a nd d epo sit, following manufacturer’s instructions, a heavy metal conductive coating on the sample.
CALIBRATION AND QUALITY CONTRO L: 10. Microscope adjustments. Follow the manufacturer’s instructions. At least once daily use an SEM performance standard, such as the NIST traceable U1011. Record in log book the results of the exa m ination of this s tand ard. 11. If more rigorous magnification calibration is needed, use a diffraction grating replica. a. Insert a m ounted diffraction grating replica into the sam ple cham ber. b. Obta in a secondary electron image of the replica and m easure the distanc e (m m ) between the same relative pos ition (e.g., between left edg es) of two widely-sepa rated lines on the grating replica . c. Mea sure the distance separated lines on the grating replica. Count the number of spaces between the lines. d. Calculate the true m agnification(M)
where: X = total distance (mm ) between the two grating lines; G = calibra tion co nsta nt of the gra ting rep lica (lines/m m ) Y = number of grating replica spaces counted.
MEASUREMENT: 12. Use s econd ary electron detector( at ~15KeV) and scan the filter at low m agnification (~100X). Observe the particulate loading. If the filter is not evenly loaded, it should not be analyzed (see note 4 below) 13. Adjust m agnification to ~1200X and find the center of the filter using the X-Y m anipulators. Fields are exa m ined at regular intervals from the cente r of the filter along a trave rse in one direction. 14. Determine the area of the viewing field at this magnification using the inscribed or overlain calibrated sca le. 15. Count fibers in each field; distinguish, based upon morphology, between cellulose and other fiber types and make note of the relative proportion of fibrous to non-fibrous material in the field. 16. Counting rules: (Modified A rules, NIOSH Method 7400).[2] a. Count any fiber longer than 5 :m (see note 2 below for exceptions) i. Count only fibers longer than 5 :m . Measu re an d rec ord len gth of fibers . ii. Count only fibers with a length-to-width ratio equal to or greater than 3:1. b. For fibers which cro ss th e bo und ary of the view ing field: i. Use the X -Y m anipulators as neede d, to follow and m easure the en tire length of any fibers that meet the criteria of rule a above. Return to original viewing field before moving to the nex t field. ii. Re ject and d o no t count all othe r fibers . c. Co unt enou gh viewing fields to yield at leas t 100 cellulos e fibers. C oun t a m inim um of 40 fields. d. W hen selecting fields, ensure that fields do not contain fibers counted and measured from a prev ious field. NOT E 1: W hen analyzing a viewing field, continuously scan a range of focal planes by moving the focus k nob to observe and m eas ure fibers which ha ve do no t lie flat on the filter.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​CEL LULO SE INS ULA TIO N: ME TH OD 7404, Issue 1, dated 1 5 Ma rch 2003 - page 4 of 6 NOT E 2:
NOT E 3: NOT E 4:
This m ethod allows for differentiation of fibers based on m orphology. Cellulose fibers are easily distinguished from asbestos and glass fibers by morphology [3]. Do not count any fibers that have parallel sides. Do no t approach c loser than 3 viewing fields from the edg e of the filter. Under certain conditions, electrostatic charge may affect the sampling of fibers. These electrostatic effects are mo st likely to occur when the relative hum idity is low (during dry applicatio n), and when sam pling is perform ed near the source of a erosol. T he res ult is that depo sition of fibers on the filter is reduc ed, espe cially near the edge of the filter. In extre m e ca ses , m uch of the sam ple m ay be a dhe ring to th e ca sse tte itself [4].
CALCULATIONS: 17. Ca lculate and repo rt fiber dens ity on the filter, E (fib/m m 2), by dividing the average fiber count per viewing field, F /n f , minus the m ean field blan k coun t per viewing field, B/n b, by the viewing field area, Af :
18. Calculate and repo rt the concentration, C (fib/mL), of cellulose fibers in the air volume sam pled, V (L), using the effective collection area of the filter, A c (approx. 385 mm 2 for a 25-m m filter):
19. Calculate and report the fiber length ranges( minimum and maximum ) as well as the average length.
EVALUATION OF METHOD: This method draws on both Methods 7400 for counting procedures and 7402 for instrumentation and setup. The m ajor difference is the counting rules have been adapted from the A rules to allow for the cou nting a nd s izing of all cellulose fibers having a 3 :1 or greate r asp ect ra tio and a leng th of at least 5 microns. There are no diameter limits as cellulose fibers are truly 3 dimensional. This is illustrated in the figure s be low. T he c om plex sha pes and con stan tly varying diam eters m ake even a n ap prox imate diam eter d eterm ination impos sible. Sam pling and analysis of both wet and dry cellulose insulation application has shown that there is much more uniform fiber deposition across the filter when the wet process is used. There is also much less fiber lost to the ca sse tte walls.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​CEL LULO SE INS ULA TIO N: ME TH OD 7404, Issue 1, dated 1 5 Ma rch 2003 - page 5 of 6
REFERENCES: [1]
[2]
[3] [4]
NIOSH [2001]. Hazard evaluation and technical assistance report: Cellulose Insulation Applicators: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, NIOSH HETA R eport No. 2000-0332-22827 NIOSH [1994]. Asbestos and Other Fibers by PCM: Method 7400. In: Eller PM, Cassinelli ME, eds. NIO SH m anu al of analytical m etho ds, 4 th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113. McCrone W and Delly J [1973]. "The Particle Atlas," Ann Arbor, MI: Ann Arbor Science. Baron P, Deye G [1990]. "Electrostatic Effects in Asbestos Sampling," Parts I and II Amer. Ind. Hyg. Assoc . J., 51, 51-69.
METHOD WRITTEN BY: Joseph E. Fernback, NIOSH/DART
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​CEL LULO SE INS ULA TIO N: ME TH OD 7404, Issue 1, dated 1 5 Ma rch 2003 - page 6 of 6 FIGURES: The figures below are examples of cellulose insulation fibers and accompanying non-fibrous cellulose.
FIGURE 1.
Figure shows many of the shapes and sizes of both fibrous and non-fibrous cellulos e insu lation.
FIGURE 2.
Figure shows the variety of shapes and sizes, as in Figure 1, as well as a glass fiber left over from the previous attic insulation.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition