Determination of partition and diffusion coefficients of formaldehyde in selected building materials and impact of relative humidity

Figures & data

Figure 1. Schematic of dual chambers (Xu and Zhang, 2011).

Figure 2. Test concentrations for conventional gypsum wallboard under 20% RH.

Figure 3. Test specimens. (a) Conventional and “green” wallboard (note: the appearance of the two kinds of wallboards were the same, since the same paint was used). (b) “Green” carpet.

Figure 4. Measured air flow rate versus pressure drop for determination of air permeability of the carpet specimen.

Table 1. Repeatability of conventional wallboard at 50% RH

	50% RH	50% RH (Repeat)	Difference	Average
D e (m^2/sec)	6.34 × 10^−8	6.61 × 10^−8	4.2%	6.48 × 10^−8
K ma	446	479	7.1%	463

Table 2. Summary of test results for wallboards

Materials	RH Condition (%)	C Ain (μg/m^3)	C Aout (μg/m^3)	C Bout (μg/m^3)	D e (m^2/sec)	K ma
Conventional wallboard	20	2662.8	2603.4	72.9	3.67 × 10^−8	304
	50	3106.0	2921.7	138.8	6.34 × 10^−8	446
	50 (repeat)	2665.9	2500.8	124.1	6.61 × 10^−8	479
	70	2443.2	2274.7	163.3	9.84 × 10^−8	404
“Green” wallboard	20	2649.5	2244.3	260.1	1.65 × 10^−7	1100
	50	2715.9	2178.8	330.2	2.24 × 10^−7	1205
	70	1591.2	1007.6	275.7	4.73 × 10^−7	1325

Figure 5. Comparison of conventional and green wallboards.

Table 3. Comparison of effective diffusion coefficient with other literature values

Reference	Material	Compound	Efective DiffusionCoeffficient (m^2/sec)
This study	Conventional gypsum wallboard	Formaldehyde	6.34 × 10^−8
	“Green” gypsum wallboard	Formaldehyde	2.24 × 10^−7
Bodalal et al. (2000)	Plywood	Cyclohexane	5.39 × 10^−8
	Floor tile	Decane	2.73 × 10^−8
Zhang et al. (2002, 2003)	Painted drywall	Ethylbenzene	2.68 × 10^−8
	Painted drywall	Benzaldehyde	4.81 × 10^−8
	Ceiling tile	Benzaldehyde	2.61 × 10^−7
	Ceiling tile	Decane	9.62 × 10^−8
Farajollahi et al. (2009)	Ceiling tile	Hexane	1.97 × 10^−6
	Ceiling tile	Octane	1.79 × 10^−6
Meininghaus et al. (2000)	Gypsum	Octane	8.40 × 10^−7
Xu and Zhang (2011)	Calcium silicate	Formaldehyde	3.28 × 10^−6
Xiong et al. (2011)	Medium density fiberboard	Formaldehyde	8.15 × 10^−8

Table 4. Summary of calculated mass fluxes in carpet tests

Specimen	Designated RH (%)	Total Mass Flux(μg/sec)	Mass Flux Due to Convection* (μg/sec)	Mass Flux Due to Diffusion(μg/sec)
“Green” carpet	20	1.31 × 10^−8	−1.78 × 10^−8	3.09 × 10^−8
	50	1.25 × 10^−8	−1.85 × 10^−8	3.10 × 10^−8
	70	1.29 × 10^−8	−3.65 × 10^−8	4.94 × 10^−8
Note: *Negative sign means that the flux is from chamber B to chamber A.

Table 5. Summary of test results for carpet

Materials	RH Condition (%)	C Ain (μg/m^3)	C Aout (μg/m^3)	C Bout (μg/m^3)	D e (m^2/sec)	K ma
“Green” carpet	20	3346.71	1825.11	1530.71	2.30 × 10^−5	471
	50	3294.84	1721.42	1451.83	2.64 × 10^−5	661
	70	3388.96	1790.57	1491.51	5.00 × 10^−5	967

Figure 6. Effective diffusion coefficients and partition coefficients of carpet at different RHs.

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