Natural Gas Appliances Research Articles

Should we use natural gas in our homes? Risk perceptions from the U.S

Multiple municipalities in the U.S. have banned natural gas hook-ups in new home construction. Several state governments have pre-empted those bans. Yet little is known about public perceptions of natural gas appliances in the home. We used survey data to evaluate risk perceptions associated with natural gas appliances and investigate potential demographic and ideological effects on risk perceptions. We find little political polarization or “white male” effects, but those who are dissatisfied with indoor air quality and concerned about climate change have heightened risk perceptions. Overall, natural gas risk perceptions are low. However, as of late 2022, the health implications of natural gas use in the home and potential mitigation policy have entered public discourse, implying that these risks may become more salient and politically charged. We conclude by discussing implications for indoor environments and policy.

Overcoming State-Level Preemption to Electrify New Buildings: a Philadelphia Case Study

The use of natural gas in heating and cooking negatively impacts environmental and human health. As government investments in clean energy production continue to increase, replacing natural gas appliances with electric alternatives is imperative to both reduce greenhouse gas emissions and protect public health. As a large US city with robust emissions reduction goals, Philadelphia, PA must significantly reduce natural gas use in buildings. However, many states, including PA, have advanced legislation that preemptively restricts municipalities from banning natural gas use. Using Philadelphia as a case study, we propose policy options, including electric appliance rebates, electrification incentives, and building efficiency standards, that US municipalities can pursue to circumvent state preemption laws in electrifying new construction, significantly reducing natural gas demand, and advancing their net-zero emissions goals.

On the initiation of blow-out from cooktop burner jets: A simplified energy-based description for the onset of laminar flame extinction in premixed hydrogen-enriched natural gas (HENG) systems

Due to the prohibitive financial expense and logistical difficulties of a wholesale changeover from natural gas to hydrogen, hydrogen-enriched natural gas (HENG) offers a more viable intermediate solution for offsetting the carbon dioxide output of domestic gas usage and reducing the blow-out susceptibility of natural gas flames. In order to formulate a practically useful description of the blow-out threshold, the present work addresses the minimum energy per unit volume of premixed gas required for the sustained combustion of HENG fuels with molar hydrogen concentrations between zero and 50 mol%. By considering a ring burner comprising circular burner jet apertures with diameters in the range 1.0–2.4 mm, this critical energy density was demonstrated to increase linearly with the mean velocity of the admitted gas premixture, approaching a value that was common to all of the investigated HENG compositions in the limit of zero flow. Furthermore, despite flame morphology varying substantially as a function of flow conditions, the visible surface area of critically stable flames consistently exhibited an empirical squared dependence on the power generated by combusting fuel. By combining these correlations, the onset of blow-out was shown to be well-approximated by a formula that relates the critical surface-averaged laminar burning velocity to the mean velocity of gas molecules at the burner jet. This model provides a simplified means of predicting blow-out conditions from measurable input parameters and could serve as an invaluable asset for the design of new HENG burner systems or the retrofitting of existing natural gas appliances.

Quantifying Methane Emissions from Natural Gas Water Heaters.

Methane emissions from natural gas appliances remain the least characterized portion of the fossil-fuel supply chain. Here we examine water heaters from 64 northern California homes to (1) quantify methane emissions from natural gas leaks and incomplete combustion while off, turning on or off, and in steady-state operation from 35 homes; and (2) characterize daily usage patterns over ∼1-2 months per water heater to estimate activity factors from 46 homes. Individual tankless water heaters emitted 2390 [95% CI: 2250, 2540] g CH4 yr-1 on average, 0.93% [0.87%, 0.99%] of their natural gas consumed, primarily from on/off pulses. Storage water heaters emitted 1400 [1240, 1560] g CH4 yr-1 on average, 0.39% [0.34%, 0.43%] of their natural gas consumption. Despite higher methane emissions, tankless water heaters generate 29% less CO2e20 than storage water heaters because they use less energy to heat a unit of water. Scaling our measured emissions by the number of storage and tankless water heaters in the United States (56.8 and 1.2 million, respectively), water heaters overall emitted an estimated 82.3 [73.2, 91.5] Gg CH4 yr-1, 0.40% [0.35%, 0.44%] of all natural gas consumed by these appliances, comparable in percentage to the EPA's estimate of methane emissions from upstream natural gas production.

Flashback, burning velocities and hydrogen admixture: Domestic appliance approval, gas regulation and appliance development

Introducing natural gas/hydrogen mixtures to an installed population of domestic natural gas appliances necessarily implies considering the risk of flashback. Previously, we quantified this risk via an interchangeability analysis using calculated laminar burning velocities. With an increasing contribution of renewable energy, still higher hydrogen fractions will become of interest to improve the economic viability in power-to-gas chains. To extend the possibilities for hydrogen admixture beyond the limits given by extant ranges of Wobbe Index and burning velocity, appliance approval standards and gas regulations must be examined to assess the degree to which higher hydrogen fractions are, or can be, justified. However, the current standards and regulations do not consider the risk of flashback in terms of the laminar burning velocity explicitly, leaving the justification of higher hydrogen fractions to empirical observations followed when the approval standards were codified. Here, we reframe the approval and regulation standards in terms of the calculated laminar burning velocity, which quantifies the notion of a ‘safety margin’ to safeguard appliance performance with respect to flashback, for a group of natural gases that is commonplace in the European Union (EU) but representative for many international situations. The method presented can be applied for any local regulatory area. In plots of burning velocity vs. equivalence ratio, ranges of regulated gas qualities are represented as a curve for natural gases, while for natural gas/hydrogen mixtures they appear as areas indicating the variations in hydrogen fraction for different gas compositions that do not increase the risk of flashback. To quantify the safety margin, the approval gas used in the EU for flashback (G222) is taken as an example, because of the many decades of experience in using this gas to safeguard appliance performance. Using the assumed range of gas quality and approval gas as an example, for appliances whose primary equivalence ratio is fuel rich (at greatest risk for flashback), a safety margin of 11.5 cm/s is determined and used in analyses for determining the composition of flashback limit gases in approval standards for a situation in which higher hydrogen fractions are desired. Situations considering both variable and constant fractions of hydrogen in natural gas are examined. The end-use demand for a minimum degree of thermal comfort, by having a minimum Wobbe Index in the regulated range of gas quality, automatically complicates grid management schemes for hydrogen addition: the maximum hydrogen admixture is necessarily coupled to the composition of the natural gas to which it is added. The only solution for having a constant hydrogen fraction without regard to the gas composition is by relaxing this demand on thermal comfort; in the example used here, 20% hydrogen admixture reduces the thermal comfort in the worst case by 4.7%. Fuel suppliers, grid operators and end users must agree to this loss of fitness for purpose to maximize the decarbonization of the gas supply by hydrogen admixture.

Unburned Methane Emissions from Residential Natural Gas Appliances.

Methane, the primary component of natural gas (NG), is a potent greenhouse gas. NG is a common fuel for residential appliances because of low cost, high energy density, and relatively clean combustion. NG exhaust contains some unburned methane due to inevitable incomplete combustion. A field campaign measuring methane concentrations in exhaust from residential NG appliances was conducted in Boston and Indianapolis to determine their contribution to overall emissions. NG space heating, water heating, and cooking appliances were measured in 100 homes. Appliance exhaust typically exhibits a brief methane concentration spike during ignition and extinguishment and relatively low concentrations during steady-state operation. Exceptions to this pattern include ovens, suboptimal stove burners, and tankless water heaters, which either have a different operating pattern or nontrivial steady-state concentrations. Findings were combined with appliance usage and prevalence assumptions to estimate total emissions. Annually, ∼30 [97.5% CI: 19-160] Gg of methane emissions can be attributed to U.S. residential NG appliances, corresponding to ∼830 [530-4500] Gg carbon dioxide equivalent (CO2e100). This accounts for ∼0.1% [0.08-0.7%] of U.S. anthropogenic methane emissions (which account for ∼10% of total U.S. greenhouse gas emissions) and corresponds to an emission factor of 0.38 g/kg of NG consumed (0.038% [0.024%-0.21%]).

Day-Ahead Optimal Joint Scheduling Model of Electric and Natural Gas Appliances for Home Integrated Energy Management

Home energy management systems (HEMSs) enable residential customers to efficiently participate in demand response programs in order to obtain optimal benefits. Traditional HEMSs only manage household electric appliances to reduce the electricity consumption cost while the optimal scheduling of natural gas appliances has been overlooked. Due to the increasing popularity of natural gas appliances in modern smart homes, the electricity consumption of residential customers connected to the natural gas network is significantly affected by the use of natural gas appliances. To consider the interaction between electric and natural gas appliances in households, a day-ahead optimal joint scheduling model of electric and natural gas appliances for HEMS is proposed. Firstly, all household appliances are classified into several categories and the mathematical model of each appliance is presented. Then, a day-ahead optimal joint scheduling model of both electric and natural gas appliances for HEMS is formulated, in which the objective function is to minimize the household's energy cost and the dissatisfaction level caused by the shifting, reduction and replacement of loads in response to the time varying prices. Case studies using realistic data indicate that the proposed model can save the total energy costs up to 30% for customers whilst ensuring their satisfaction levels.

Hydrogen-enriched natural gas as a domestic fuel: an analysis based on flash-back and blow-off limits for domestic natural gas appliances within the UK

In the effort to reduce carbon emissions from an ever-increasing global population, it has become increasingly vital to monitor and counteract the environmental impact of our domestic energy usage given its contribution to overall carbon emissions.

The impact of natural gas/hydrogen mixtures on the performance of end-use equipment: Interchangeability analysis for domestic appliances

The addition of hydrogen derived from renewable power to the natural gas network is being promoted as a viable means of storing excess wind and solar energy. However, the changes in combustion properties of the natural gas upon hydrogen addition can impact the performance of the end-use equipment connected to the gas grid. We assess the changes in safety and fitness for purpose of domestic natural gas appliances when supplied with natural gas/hydrogen mixtures. Upon hydrogen addition, the fitness-for-purpose limits are governed by changes in thermal input caused by changes in Wobbe Index, while the changes in risk of flashback are used to quantify the safety aspects. A method is introduced to assess changes in the propensity for flashback, using the computed laminar burning velocity and accounting for changes in equivalence ratio caused by the variations in fuel composition. The computations are seen to reflect the experimental behavior of Bunsen flames regarding flashback upon hydrogen addition to natural gas accurately. Comparing the changes in Wobbe Index and variations in burning velocity with those experienced by domestic appliances subjected to the range of natural gases ordinarily distributed to the end user provides an unambiguous and internally consistent method to assess changes in essential performance upon hydrogen addition. Thus, limits on hydrogen addition can be derived to maintain the current level of safety and fitness for purpose without the necessity of large-scale appliance testing. The results show that the maximum fraction of hydrogen in natural gas that maintains appliance performance depends on the composition of the natural gas to which the hydrogen is added. For fuel-rich premixed appliances, e.g., cooking burners, the maximum hydrogen admixture is seen to be limited by flashback, while loss of thermal input determines the maximum hydrogen fraction in modern lean-premixed appliances. The method is illustrated using a fictitious distribution band, but it can be applied to any regional or national situation. The method presented can be used to define efficient strategic roadmaps and provides essential knowledge for grid management assessments, aimed at introducing hydrogen into the natural gas infrastructure while maintaining performance for the end user.

Preliminary assessment of BTEX concentrations in indoor air of residential buildings and atmospheric ambient air in Ardabil, Iran

BTEX concentrations in indoor and outdoor air of 50 homes were studied in Ardabil city and their influencing parameters including; heating system, using gas stove and samovar, tobacco smoking, the floors in which the monitored homes were located, and kitchen plan were considered in the study. Risk assessment analysis was carried out with the obtained concentrations based on EPA IRIS reference doses. BTEX compounds were sampled by charcoal tubes and the samples were analyzed by a GC-FID. Concentrations of benzene (15.18 μg/m3 vs. 8.65 μg/m3), toluene (69.70 μg/m3 vs. 40.56 μg/m3), ethylbenzene (12.07 μg/m3 vs. 4.92 μg/m3) and xylene (48.08 μg/m3 vs. 7.44 μg/m3) in indoor air were significantly (p < 0.05) higher than the levels quantified for outdoor air. The obtained concentrations of benzene were considerably higher than the recommended value of 5 μg/m3 established by Iran environmental protection organization. Among the BTEX compounds, benzene (HQ = 0.51) and xylene (HQ = 0.47) had notable hazard quotient and were the main pollutants responsible for high hazard index in the monitored homes (HI = 1.003). The results showed considerably high cancer risk for lifetime exposure to the indoor (125 × 10−6) and outdoor (71 × 10−6) benzene. Indoor benzene concentrations in homes were significantly influenced by type of heating system, story, and natural gas appliances.

Indoor air pollution associated with the use of natural gas appliances in households in Bogota, Colombia: levels and determinants

Levels and determinants of indoor carbon monoxide (CO) pollution were characterised in a pilot sample of households in Bogota, Colombia, in which natural gas appliances (NGA) were frequently used. Real-time CO concentration measurements were conducted using Langan T15 electrochemical cells in kitchen and living rooms, at 73 homes. Results show that the use of NGA has a direct impact on indoor air quality with CO concentrations ranging between 5 and 150 parts-per-million. In 14 out of the 73 homes, CO concentrations were above the World Health Organization standards during at least 10% of the day. This is a matter of concern for local public health authority since the number of reported cases of CO involuntary intoxications in the city has significantly increased since 2008. Evidence presented hereby has important implications in regard to NGA installation standards and housing polices (especially in the case of low income dwelling). It urges to involve healthy-house concepts in building codes, to prevent inadequate indoor air quality and to improve people living conditions.

Results of the California Healthy Homes Indoor Air Quality Study of 2011-2013: impact of natural gas appliances on air pollutant concentrations.

This study was conducted to assess the current impact of natural gas appliances on air quality in California homes. Data were collected via telephone interviews and measurements inside and outside of 352 homes. Passive samplers measured time-resolved CO and time-integrated NOX , NO2 , formaldehyde, and acetaldehyde over ~6-day periods in November 2011 - April 2012 and October 2012 - March 2013. The fraction of indoor NOX and NO2 attributable to indoor sources was estimated. NOX , NO2 , and highest 1-h CO were higher in homes that cooked with gas and increased with amount of gas cooking. NOX and NO2 were higher in homes with cooktop pilot burners, relative to gas cooking without pilots. Homes with a pilot burner on a floor or wall furnace had higher kitchen and bedroom NOX and NO2 compared to homes without a furnace pilot. When scaled to account for varying home size and mixing volume, indoor-attributed bedroom and kitchen NOX and kitchen NO2 were not higher in homes with wall or floor furnace pilot burners, although bedroom NO2 was higher. In homes that cooked 4h or more with gas, self-reported use of kitchen exhaust was associated with lower NOX , NO2 , and highest 1-h CO. Gas appliances were not associated with higher concentrations of formaldehyde or acetaldehyde.

A model of residential energy end-use in Canada: Using conditional demand analysis to suggest policy options for community energy planners

Abstract We applied conditional demand analysis (CDA) to estimate the average annual energy use of various electrical and natural gas appliances, and derived energy reductions associated with certain appliance upgrades and behaviours. The raw data came from 9773 Canadian households, and comprised annual electricity and natural gas use, and responses to >600 questions on dwelling and occupant characteristics, appliances, heating and cooling equipment, and associated behaviours. Replacing an old (>10 years) refrigerator with a new one was estimated to save 100 kW h/year; replacing an incandescent lamp with a CFL/LED lamp was estimated to save 20 kW h/year; and upgrading an old central heating system with a new one was estimated to save 2000 kW h/year. This latter effect was similar to that of reducing the number of walls exposed to the outside. Reducing the winter thermostat setpoint during occupied, waking hours was estimated to lower annual energy use by 200 kW h/°C-reduction, and lowering the thermostat setting overnight in winter relative to the setting during waking hours (night-time setback) was estimated to have a similar effect. This information may be used by policy-makers to optimize incentive programs, information campaigns, or other energy use change instruments.

Environmental and occupational allergies

Airborne allergens are the major cause of allergic rhinitis and asthma. Daily exposure comes from indoor sources, chiefly at home but occasionally at schools or offices. Seasonal exposure to outdoor allergens, pollens, and molds is another important source. Exposure to unusual substances at work causes occupational asthma, accounting for about 5% of asthma in adults. Indoor and outdoor air pollutants trigger airway inflammation and increase the severity of asthma. Diesel exhaust particles increase the production of IgE antibodies. Identification and reduction of exposure to allergens is a very important part of the management of respiratory allergic diseases. The first section of this chapter discusses domestic allergens, arthropods (mites and cockroaches), molds, and mammals (pets and mice). Indoor humidity and water damage are important factors in the production of mite and mold allergens, and discarded human food items are important sources of proliferation of cockroaches and mice. Means of identifying and reducing exposure are presented. The second section discusses outdoor allergens: pollens and molds. The particular plants or molds and the amount of exposure to these allergens is determined by the local climate, and local pollen and mold counts are available to determine the time and amount of exposure. Climate change is already having an important effect on the distribution and amount of outdoor allergens. The third section discusses indoor and outdoor air pollution and methods that individuals can take to reduce indoor pollution in addition to eliminating cigarette smoking. The fourth section discusses the diagnosis and management of occupational asthma.

Transformations, Lifetimes, and Sources of NO2, HONO, and HNO3in Indoor Environments

Recent research has demonstrated that nitrogen oxides are transformed to nitrogen acids in indoor environments, and that significant concentrations of nitrous acid are present in indoor air. The purpose of the study reported in this paper has been to investigate the sources, chemical transformations and lifetimes of nitrogen oxides and nitrogen acids under the conditions existing in buildings. An unoccupied single family residence was instrumented for monitoring of NO, NO2, NOy, HONO, HNO3, CO, temperature, relative humidity, and air exchange rate. For some experiments, NO2 and HONO were injected into the house to determine their removal rates and lifetimes. Other experiments investigated the emissions and transformations of nitrogen species from unvented natural gas appliances. We determined that HONO is formed by both direct emissions from combustion processes and reaction of NO2 with surfaces present indoors. Equilibrium considerations influence the relative contributions of these two sources to the indoor burden of HONO. We determined that the lifetimes of trace nitrogen species varied in the order NO approximately HONO > NO2 > HNO3. The lifetimes with respect to reactive processes are on the order of hours for NO and HONO, about an hour for NO2, and 30 minutes or less for HNO3. The rapid removal of NO2 and long lifetime of HONO suggest that HONO may represent a significant fraction of the oxidized nitrogen burden in indoor air.

Carboxyhemoglobin levels in children with nonspecific flu-like symptoms

Although carbon monoxide intoxication is thought to account for approximately half of all deaths caused by poisons] the incidence of sublethal toxicity has not been well investigated in a pediatric population. The manifestations of CO poisoning may be severe or subtle. 24 Commo nly, signs and symptoms are gradual and simulate other illnesses.? ,3.5 Flu-like symptoms such as headache, dizziness, weakness, nausea, vomiting, and drowsiness are frequent? The purpose of our study was to determine the possibility of carbon monoxide poisoning as a cause of nonspecific flu-like symptoms in children who had no recognized exposure. METHODS Children younger than 18 years of age, consecutively seen in The Children's Hospital of Philadelphia Emergency Department for evaluation of flu-like symptoms (headache, dizziness, weakness, nausea, vomiting, altered mental status), were eligible for entry into the study. Excluded were patients with symptoms specifically suggestive of a viral illness, including fever >38.9 ~ C, watery stools, viral exanthem or enanthem, or with a history of smoke inhalation. Enrollees were also required to have one or more exPosure criteria, including the occurrence of symptoms while (1) a motor vehicle passenger; (2) a resident of a home with combustible fuel heat, including kerosene heaters, wood stoves, fireplaces, natural gas appliances, Sterno units, or central heating systems older than 10 years; or (3) exposed to chemical fumes such as those generated by paint strippers.