Monitoring of carbon monoxide in residences with bulk wood pellet storage in the Northeast United States

Figures & data

Table 1. Summary of regulatory and recommended exposure limits for carbon monoxide.

Limit/level	Type	Organization	Residential/industry
9 ppm^1	TWA	U.S. EPA	General
9 ppm^2	TWA	WHO	General (outdoor)
9 ppm^3	Ceiling	ASHRAE	General (living areas)
25 ppm^4	TWA	ACGIH	Work environment
35 ppm^5	TWA	NIOSH	Work environment
50 ppm^6	OSHA PEL as TWA	OSHA	Work environment

Note. Information sources:

1. National Ambient Air Quality Standards (NAAQS). 2011. http://www.epa.gov/air/criteria.html (accessed August 21, 2015).

2. World Health Organization (WHO). 1999. Environmental Health Criteria 213, Carbon Monoxide, 2nd ed. http://www.who.int/ipcs/publications/ehc/en/ehc_213_part_1.pdf, page 19.

3. ASHRAE-62.1. 2013. Ventilation for Acceptable Indoor Air Quality—Appendix B. ASHRAE-62.1-2013.

4. 2014 ACGIH Handbook of TLVs and BEIs. 2004.

5. National Institute for Occupational Safety and Health (NIOSH). 2009. http://www.cdc.gov/niosh-rtecs/FG3567E0.htm (accessed August 21, 2015).

6. Occupational Safety & Health Administration. 2006. Carbon monoxide. http://www.osha.gov/dts/chemicalsampling/data/CH_225600.html (accessed August 21, 2015).

Table 2. Characteristics of the homes included in the study.

House number	Year^a	Basement/pellet storage room^b	Air tightness	Dampness	Gas-powered equipment/other potential CO sources	Location of garage^c
Controls
2	1923	Unfinished	Drafty	Dry to slightly damp	Oil boiler, gas dryer and water heater, snow blower	None
4	1960s	Finished	Tight	Dry	Propane furnace, wood stoves, gas dryer	Detached
6	1976	—	Tight to average	Dry	Water heater	Not attached to basement
7	1979	—-	Average to not tight	Damp in spring		Detached
Outdoor
9	1984	Outdoor pellet storage room^d	Not tight	Dry	Only pellet storage	Detached
15	1983	(40-lb bags in garage)	NA	Dry		Detached
17	1837	Outdoor pellet storage room	Tight	Dry	None	Detached
20	2013	Fabric bin outdoors	Average to not tight	Damp	None	Detached
Indoor^e
3	1990	Unfinished	Tight to average	Dry	Propane dryer	Attached to pellet storage area
5	1964	Unfinished	Tight	Dry	—	Detached
8	2012	Finished	Tight	Dry	Motorcycle storage	Pellets stored below garage
10	1900	Unfinished	Tight	Somewhat Damp	Wood stove, water heater	Detached
11	1976	Unfinished	Tight	Dry	none	Basement below garage
12	1962	Unfinished	Tight to average	Dry	Large ATV, snow blower, mower	Attached to pellet storage area
13	2004	Unfinished	Tight to average	Dry	None	Detached
14	1930	Unfinished	A bit drafty	Damp	Radiator	Detached
16	1952	Utility room	Average	Damp	Dryer, water heater	Detached
18	2013	Utility Room	Tight	Dry	None	Not attached near storage
19	1988	Unfinished	Average to not tight	Damp	None	None
21	1950s	Unfinished	Tight	Somewhat damp	Water heater	Not attached near storage
22	1774/2002	Unfinished	Tight	Somewhat damp	Fireplace outlet	Detached
23	1951	Unfinished	Tight	Somewhat damp	None	Not attached near storage
24	1979	Unfinished	Tight	Dry	None	Detached
25	1994	Finished	Average to not tight	Somewhat damp	None	None

^aAll homes single family, except house 2, which was a two-family residence

^bAll unfinished basements had cement floors (i.e., dirt floors were polled, none reported). None of the pellet storage units used active ventilation (e.g., fans).

^c”Detached” garages not attached to the house; the location of attached garages relative to the pellet storage is noted.

^dMonitors in outdoor storage room, not near boiler.

^eAll indoor storage used “synthetic canvas bag” except for 19 and 23 with plywood storage bins, and 22 reported “rip stop nylon bag.”

Figure 1. A typical wood storage container (bag) used for storage of bulk pellets. The temperature and CO monitors are shown in the upper left corner.

Table 3. Mean ± standard deviation of the CO concentrations in ppm measured by each monitor over approximately 1-hr intervals for each calibrated CO test. Note. The calibration concentrations are shown as the column headings. No calibration data are available for CO monitors 1, 18, and 24.

CO monitor number	0.5 ppm CO	3.3 ppm CO	9.5 ppm CO	17.4 ppm CO	24.2 ppm CO
2	1.5 ± 0.0	4.5 ± 0.1	11.4 ± 0.2	19.5 ± 0.2	25.6 ± 0.2
3	0.5 ± 0.0	3.0 ± 0.0	8.7 ± 0.2	16.1 ± 0.4	22.4 ± 0.2
4	0.6 ± 0.2	3.6 ± 0.2	10.3 ± 0.2	19.7 ± 0.4	27.6 ± 0.4
5	0.0 ± 0.0	1.0 ± 0.1	6.5 ± 0.0	12.3 ± 0.3	17.0 ±0.0
6	0.0 ± 0.0	2.4 ± 0.2	8.3 ± 0.3	15.3 ± 0.3	20.9 ± 0.4
7	3.0 ± 0.1	6.0 ± 0.1	13.2 ± 0.3	22.3 ± 0.3	29.6 ± 0.2
8	2.0 ± 0.0	4.5 ± 0.1	10.3 ± 0.3	18.6 ± 0.3	25.3 ± 0.5
9	1.5 ± 0.1	3.8 ± 0.2	8.8 ± 0.3	14.8 ± 0.3	19.6 ±0.2
10	1.0 ± 0.0	3.0 ± 0.0	7.8 ± 0.2	13.7 ± 0.3	18.4 ± 0.2
11	0.0 ± 0.0	2.3 ± 0.2	7.7 ± 0.4	15.4 ± 0.2	21.1 ± 0.2
12	0.2 ± 0.2	3.0 ± 0.1	9.4 ± 0.2	17.2 ± 0.3	23.9 ± 0.2
13	0.0 ± 0.0	3.0 ± 0.1	9.3 ± 0.3	17.9 ± 0.4	25.0 ± 0.0
14	0.0 ± 0.0	0.8 ± 0.2	5.6 ± 0.2	12.2 ± 0.3	17.6 ± 0.3
15	1.0 ± 0.0	4.0 ± 0.1	10.0 ± 0.0	16.9 ± 0.2	22.4 ± 0.2
16	1.5 ± 0.0	4.4 ± 0.2	11.3 ± 0.2	19.5 ± 0.1	26.1 ± 0.2
17	0.5 ± 0.0	4.2 ± 0.3	12.4 ± 0.3	23.1 ± 0.2	31.3 ± 0.3
19	0.5 ± 0.1	3.5 ± 0.1	10.2 ± 0.3	19.0 ± 0.3	25.8 ± 0.3
20	0.0 ± 0.0	1.6 ± 0.2	6.5 ± 0.0	13.0 ± 0.0	18.0 ± 0.0
21	0.0 ± 0.0	2.0 ± 0.1	8.0 ± 0.0	15.8 ± 0.3	22.4 ± 0.2
22	0.0 ± 0.0	1.3 ± 0.3	5.5 ± 0.0	10.5 ± 0.0	14.5 ± 0.0
23	0.9 ± 0.2	3.8 ± 0.3	10.4 ± 0.2	19.1 ± 0.3	26.0 ± 0.0
25	0.0 ± 0.0	3.5 ± 0.1	10.5 ± 0.1	19.8 ± 0.3	26.9 ± 0.2

Figure 2. Histograms showing the frequency distributions for CO monitors in the laboratory and control homes. Measurements resolution was 5 min. Black lines demarcate complete bins up to and including 9 ppm (to the left) and greater concentrations (to the right).

Figure 3. Histograms showing the frequency distributions for CO monitors in the homes with outdoor pellet storage. Black lines demarcate complete bins up to and including 9 ppm (to the left) and greater concentrations (to the right).

Figure 4. Histograms showing the frequency distributions for CO monitors in the homes (3, 5, 8, 10–14) with indoor pellet storage. Black lines demarcate complete bins up to and including 9 ppm (to the left) and greater concentrations (to the right).

Figure 5. Histograms showing the frequency distributions for CO monitors in the homes (16, 18, 19, 21–25) with indoor pellet storage. Black lines demarcate complete bins up to and including 9 ppm (to the left) and greater concentrations (to the right).

Figure 6. Example calibrated final CO and temperature (T) time series plots for the Controls homes. The CO is identified with blue curves (left axes) and T with gray curves (right axes).

Figure 7. Example plots of calibrated final CO (red curves, left axes) and T (gray curves, right axes) time series for homes with indoor pellet storage where levels of CO exceeded 9 ppm. Final CO (red curves, left axes) and T (gray curves, right axes) data for homes with indoor pellet storage. The 9-ppm threshold is approximately denoted by a horizontal dashed black line in each panel. Pellet deliveries are denoted by asterisks indicating the date of delivery. Not all participants provided pellet delivery information.