Containment of procedure-associated aerosols by an extractor tent: effect on nebulized drug particle dispersal.

BACKGROUND: Several medical procedures involving the respiratory tract are considered as 'aerosol-generating procedures'. Aerosols from these procedures may be inhaled by bystanders, and there are consequent concerns regarding the transmission of infection or, specific to nebulized therapy, secondary drug exposure. AIM: To assess the efficacy of a proprietary high-efficiency-particulate-air-filtering extractor tent on reducing the aerosol dispersal of nebulized bronchodilator drugs. METHODS: The study was conducted in an unoccupied outpatient room at St. James's Hospital, Dublin, Ireland. A novel real-time, fluorescent particle counter, the Wideband Integrated Bioaerosol Sensor (WIBS), monitored room air continuously for 3 h. Baseline airborne particle count and count during nebulization of bronchodilator drug solutions were recorded. FINDINGS: Nebulization within the tent prevented any increase over background level. Nebulization directly into room air resulted in mean fluorescent particle counts of 4.75 x 105/m3 and 4.21 x 105/m3 for Ventolin and Ipramol, respectively, representing more than 400-fold increases over mean background level. More than 99.3% of drug particles were <2 µm in diameter and therefore small enough to enter the lower respiratory tract. CONCLUSION: The extractor tent was completely effective for the prevention of airborne spread of drug particles of respirable size from nebulized therapy. This suggests that extractor tents of this type would be efficacious for the prevention of airborne infection from aerosol-generating procedures during the COVID-19 pandemic.

Cirugía laparoscópica en tiempos de COVID-19 / Laparoscopic surgery in the COVID-19 era

La convivencia con la infección por COVID-19 (coronavirus disease 2019) en todos los entornos hospitalarios y de salud supone un reto actual de adaptación, creación de circuitos, protocolos y nuevos modelos de asistencia. Son todavía bastantes las incógnitas a resolver sobre esta infección en la actualidad, y mucho más desconocido es el impacto que la misma supone si lo trasladamos al terreno quirúrgico. La evidencia respecto al efecto del SARS-CoV-2 y cirugía laparoscópica es escasa y de calidad limitada, pero aun así, la laparoscopia ha sido considerada de elección por las distintas sociedades científicas en pacientes COVID para la mayoría de indicaciones en ginecología, por las conocidas ventajas hacia el paciente respecto a la vía abierta: menor morbilidad y estancia hospitalaria y porque comporta procedimientos quirúrgicos autónomos y contenidos respecto a la liberación de humo y donde, además, el instrumental y la disposición en quirófano permiten un alejamiento del cirujano y del resto de profesionales en el área quirúrgica respecto al paciente. A modo global, las dos recomendaciones fundamentales en quirófano de cirugía laparoscópica en esta época COVID incluyen: el uso de equipo de protección personal adecuado para el personal de quirófano y la adopción de precauciones para reducir la exposición al CO2 y el humo quirúrgico que puede producirse en estos procedimientos

Coexistence with COVID-19 infection (coronavirus disease 2019) in all hospital and health care settings is a current challenge of adaptation, as well as the creation of new protocols and care models. At present, there are still many unknowns about this infection, and much more unknown is the impact into the surgical field. Although evidence regarding the effect of SARS-CoV-2 and laparoscopic surgery is scarce, laparoscopy has been considered the method of choice by different scientific societies for most indications in gynaecology during the COVID-19 pandemic. This is due to the advantages over the open route. There is less morbidity and hospital stay, and in addition, as it involves autonomous and contained surgical procedures with respect to smoke release. Moreover, the instruments and the setting in the operating room mean that there can be safe distance from the surgeon and other staff to the patient. Overall, the main recommendations in laparoscopic surgery during the COVID era include: the use of Personal Protective Equipment for operating room personnel, and the adoption of safety measures to reduce CO2 exposure and surgical smoke reléase

Design Features in Multiple Generations of Electronic Cigarette Atomizers.

The design of electronic cigarette (EC) atomizing units has evolved since their introduction over 10 years ago. The purpose of this study was to evaluate atomizer design in ECs sold between 2011-2017. Atomizers from 34 brands representing three generations of ECs were dissected and photographed using a stereoscopic microscope. Five distinct atomizer design categories were identified in first generation products (cig-a-like/cartomizer) and three categories were found in the third generation. Atomizers in most cig-a-like ECs contained a filament, thick wire, wire joints, air-tube, wick, sheath, and fibers, while some later models lacked some of these components. Over time design changes included an increase in atomizer size; removal of solder joints between wires; removal of Polyfil fibers; and removal of the microprocessor from Vuse. In second and third generation ECs, the reservoirs and batteries were larger, and the atomizing units generally lacked a thick wire, fibers, and sheath. These data contribute to an understanding of atomizer design and show that there is no single design for ECs, which are continually evolving. The design of the atomizer is particularly important as it affects the performance of ECs and what transfers into the aerosol.

Determination of Passive Dry Powder Inhaler Aerodynamic Particle Size Distribution by Multi-Stage Cascade Impactor: International Pharmaceutical Aerosol Consortium on Regulation & Science (IPAC-RS) Recommendations to Support Both Product Quality Control and Clinical Programs.

The multi-stage cascade impactor (CI) is the mainstay method for the determination of the aerodynamic particle size distribution (APSD) of aerosols emitted from orally inhaled products (OIPs). CIs are designed to operate at a constant flow rate throughout the measurement process. However, it is necessary to mimic an inhalation maneuver to disperse the powder into an aerosol when testing passive dry powder inhalers (DPIs), which constitute a significant portion of available products in this inhaler class. Methods in the pharmacopeial compendia intended for product quality assurance initiate sampling by applying a vacuum to the measurement apparatus using a timer-operated solenoid valve located downstream of the CI, resulting in a period when the flow rate through the impactor rapidly increases from zero towards the target flow rate. This article provides recommendations for achieving consistent APSD measurements, including selection of the CI, pre-separator, and flow control equipment, as well as reviewing considerations that relate to the shape of the flow rate-sampling time profile. Evidence from comparisons of different DPIs delivering the same active pharmaceutical ingredients (APIs) is indicative that the compendial method for APSD measurement is insensitive as a predictor of pharmacokinetic outcomes. Although inappropriate for product quality testing, guidance is therefore provided towards adopting a more clinically realistic methodology, including the use of an anatomically appropriate inlet and mimicking patient inhalation at the DPI while operating the CI at constant flow rate. Many of these recommendations are applicable to the testing of other OIP classes.

A systematic review of experimental animal studies on microbial bioaerosols: Dose-response data for the derivation of exposure limits.

Although exposure to high levels of microbial bioaerosols can be linked to the deterioration of the human respiratory system, precise exposure levels responsible for such effects are still unknown. A previous systematic review concluded that there was not enough information in the studies in humans to derive an exposure-response relationship. Thus, the aim of this systematic review was to derive exposure limits for microbial bioaerosols based on health effects in experimental animal studies. A systematic search was done in MEDLINE (PubMed) for long-term in vivo exposure of the respiratory system via inhalation of a quantified microbial bioaerosol. A total of n = 301 studies were retrieved. Abstract screening using predefined inclusion and exclusion criteria was followed by full-text screening and standardized data extraction of study characteristics and measured outcomes. As a result, four suitable studies were identified where mice or guinea pigs were exposed for 4-12 weeks to a previously described mixture of fungal spores or conidia via inhalation. The number of macrophages, neutrophils, eosinophils and lymphocytes following subchronic exposure has been reported by all included papers and suggested a dose- and time-dependent relationship. Significant inflammation was observed following subacute exposure to Aspergillus fumigatus. However, the outcomes of the studies could not be directly compared due to the large degree of variation and poor description of the exposure conditions. It is our conclusion that more experimental research needs to be done with the specific aim of establishing a No-Observed-Adverse-Effect Level (NOAEL) and a Lowest-Observed-Adverse-Effect Level (LOAEL) for exposure to microbial bioaerosols in ambient air. Expertise of both exposure and outcome assessment should be brought together to enable standardization of experimental animal studies with properly generated aerosols aiming to derive health-based exposure limits.

Accuracy of commercial electronic nicotine delivery systems (ENDS) temperature control technology.

OBJECTIVES: For electronic nicotine delivery systems (ENDS), also commonly called e-cigarettes, coil temperature is a factor in the potential production of toxic chemical constituents. However, data are lacking regarding the temperatures that are achieved in the latest generation of these devices. Fourth-generation ENDS are capable of producing heating coil temperatures well above e-liquid boiling points, and allow the user to monitor and set the heating coil temperature during a puff. In this study, we evaluate the accuracy and consistency of the temperature measurement and control settings for different brands of fourth-generation ENDS. METHODS: A study was performed using three commercially available, fourth-generation ENDS. The atomizer coil temperatures were obtained from the device (using the EScribe software) reading and from thermocouples attached to the coils during simulated puffing conditions. In addition, aerosol temperatures were measured inside the atomizer and at the mouthpiece. RESULTS: Measured temperatures varied widely across samples taken from the same brand. For example, thermocouple measurements for one unit were 40 Celsius (°C) below the 300 °C set point, while another unit of the same brand exceeded the set point by more than 100 °C. We observed a significant variation in temperature (approximately 100 °C) along the length of the coil in some cases. CONCLUSIONS: The possibility of wide temperature variation across ENDS samples, as well as variations between maximum coil temperatures and internal temperature readings, may have implications for studies that seek to determine correlations between coil temperature and toxin generation.

European Regulatory Developments for Orally Inhaled and Nasal Drug Products.

Orally inhaled and nasal drug products (OINDP) are regulated in Europe via national (country) legislation and guidelines and/or legislation established in the European Union and resulting guidelines developed by the European Medicines Agency (EMA). Recent movement in EMA guidance and European Commission legislation implies potential significant changes in OINDP regulation. The UK exiting the European Union ("Brexit") has also raised a number of questions related to OINDP development and regulation in the region. The International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) European outreach working group provides and overview and analysis of the current state of European regulatory activity for OINDP (International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) 2018).

[Inhaled chemotherapy - Part 2: Clinical practice and potential applications]. / La chimiothérapie inhalée ­ partie 2 : clinique et applications potentielles.

Lung tumours have a high incidence and cause many deaths worldwide. Despite progresses in treatment with targeted therapies and immunotherapies, the global 5-year survival rate remains low. In this context, inhaled chemotherapy could provide a means to intensify current therapeutic modalities. This review is based on clinical studies of inhaled chemotherapy against lung tumours. The advantages of this approach in terms of pharmacokinetic ratio and therapeutic index are presented as well as the limitations including contraindications and pulmonary side effects. Moreover, the challenges linked to technical aspects around administration are identified (inhalation device and facilities to limit aerosol propagation and exposure of healthcare professionals). The current developments proposed to overcome these challenges are described briefly. Also discussed are the potential applications for the distribution of the inhaled anticancer drug into tumour-bearing respiratory tracts and finally the potential indications for current therapeutic modalities.

Inhalation device requirements for patients' inhalation maneuvers.

BACKGROUND: Inhaled drugs are the mainstay of treatment for lung diseases such as asthma and chronic obstructive pulmonary disease. However, failure to use inhalation devices correctly can lead to a poorly controlled status. A vast number of inhalation devices exist and each device has specific requirements to achieve optimum inhalation of the drug. Currently, there is no overview of inhalation requirements considering all devices. This article presents a review of the literature on different inhalation device requirements and incorporates the data into a new inhalation flow algorithm. METHODS: Data from literature on commercially available inhalation devices were evaluated and parameters, such as inhalation flow rate, flow acceleration, inhalation volume, and inspiration time assessed for the required inhalation maneuver specific to the device. All agreed upon data points were used to develop an inhalation flow algorithm. RESULTS: The literature analysis revealed availability of robust data for the required inhalation flow characteristics for most devices and thus for the development of an algorithm. For those devices for which these parameters are not published, the minimum required flow criteria were defined based on published data regarding individual aspects of aerosol quality. CONCLUSIONS: This review provides an overview of inhalation devices available on the market regarding requirements for an acceptable inhalation maneuver and shows which goals should be achieved in terms of inhalation flows. The presented algorithm can be used to develop a new computer based measurement system which could help to test and train patients' individual inhalation maneuvers with their inhalation devices.

Estimation of the Human Extrathoracic Deposition Fraction of Inhaled Particles Using a Polyurethane Foam Collection Substrate in an IOM Sampler.

Extrathoracic deposition of inhaled particles (i.e., in the head and throat) is an important exposure route for many hazardous materials. Current best practices for exposure assessment of aerosols in the workplace involve particle size selective sampling methods based on particle penetration into the human respiratory tract (i.e., inhalable or respirable sampling). However, the International Organization for Standardization (ISO) has recently adopted particle deposition sampling conventions (ISO 13138), including conventions for extrathoracic (ET) deposition into the anterior nasal passage (ET1) and the posterior nasal and oral passages (ET2). For this study, polyurethane foam was used as a collection substrate inside an inhalable aerosol sampler to provide an estimate of extrathoracic particle deposition. Aerosols of fused aluminum oxide (five sizes, 4.9 µm-44.3 µm) were used as a test dust in a low speed (0.2 m/s) wind tunnel. Samplers were placed on a rotating mannequin inside the wind tunnel to simulate orientation-averaged personal sampling. Collection efficiency data for the foam insert matched well to the extrathoracic deposition convention for the particle sizes tested. The concept of using a foam insert to match a particle deposition sampling convention was explored in this study and shows promise for future use as a sampling device.

Influence of indoor microbial aerosol on the welfare of meat ducks.

The aim of the study was to evaluate the effects of microbial aerosols on ducks' welfare and provide information on which to establish microbial aerosol concentration standards for poultry. A total of 1800 1-d-old Cherry Valley ducks were randomly divided into 5 groups (A, B, C, D and E) with 360 ducks in each. To obtain objective data, each group had three replications. Different microbial aerosol concentrations in different groups were created by controlling ventilation and bedding cleaning frequency. Group A was the control group and hygienic conditions deteriorated progressively from group B to E. A 6-stage Andersen impactor was used to detect the aerosol concentration of aerobes, fungi, gram-negative bacteria and an AGI-30 microbial air sampler detected endotoxins. Physiological stress was evaluated in the ducks by adrenocorticotropic hormone (ACTH) values in serum. To assess the effects of bioaerosol factors, welfare indicators including fluctuating asymmetry (FA), appearance and gait as well as the Lactobacillus caecal concentration were evaluated. The data showed group D had already reached the highest limit of concentration of airborne aerobic bacteria, airborne fungi, airborne gram-negative bacteria and airborne endotoxin. The ducks in this group had significantly increased serum ACTH values and significantly decreased caecal lactobacilli concentration. Furthermore, appearance and gait scores, wing length and overall FA and caecal Lactobacillus concentration in this group were significantly increased at 6 and 8 weeks of age. In conclusion, high concentrations of microbial aerosol adversely affected the welfare of meat ducks. The microbial aerosol values in group D suggest a preliminary upper limit concentration of bioaerosols in ambient air for healthy meat ducks.

Precautionary Practices of Respiratory Therapists and Other Health-Care Practitioners Who Administer Aerosolized Medications.

BACKGROUND: Respiratory therapists (RTs) and other health-care workers are potentially exposed to a variety of aerosolized medications. The National Institute for Occupational Safety and Health (NIOSH) Health and Safety Practices Survey of Healthcare Workers describes current exposure control practices and barriers to using personal protective equipment during administration of selected aerosolized medications. METHODS: An anonymous, multi-module, web-based survey was conducted among members of health-care professional practice organizations representing RTs, nurses, and other health-care practitioners. A module on aerosolized medications included submodules for antibiotics (amikacin, colistin, and tobramycin), pentamidine, and ribavirin. RESULTS: The submodules on antibiotics, pentamidine, and ribavirin were completed by 321, 227, and 50 respondents, respectively, most of whom were RTs. The relatively low number of ribavirin respondents precluded meaningful interpretation of these data and may reflect the rare use of this drug. Consequently, analysis focused on pentamidine, classified by NIOSH as a hazardous drug, and the antibiotics amikacin, colistin, and tobramycin, which currently lack authoritative safe handling guidelines. Respondents who administered pentamidine were more likely to adhere to good work practices compared with those who administered the antibiotics. Examples included training received on safe handling procedures (75% vs 52%), availability of employer standard procedures (82% vs 55%), use of aerosol delivery devices equipped with an expiratory filter (96% vs 53%) or negative-pressure rooms (61% vs 20%), and always using respiratory protection (51% vs 13%). CONCLUSIONS: Despite the availability of safe handling guidelines for pentamidine, implementation was not universal, placing workers, co-workers, and even family members at risk of exposure. Although the antibiotics included in this study lack authoritative safe handling guidelines, prudence dictates that appropriate exposure controls be used to minimize exposure to the antibiotics and other aerosolized medications. Employers and employees share responsibility for ensuring that precautionary measures are taken to keep exposures to all aerosolized medications as low as practicable.

Ventilation Rates and Airflow Pathways in Patient Rooms: A Case Study of Bioaerosol Containment and Removal.

Most studies on the transmission of infectious airborne disease have focused on patient room air changes per hour (ACH) and how ACH provides pathogen dilution and removal. The logical but mostly unproven premise is that greater air change rates reduce the concentration of infectious particles and thus, the probability of airborne disease transmission. Recently, a growing body of research suggests pathways between pathogenic source (patient) and control (exhaust) may be the dominant environmental factor. While increases in airborne disease transmission have been associated with ventilation rates below 2 ACH, comparatively less data are available to quantify the benefits of higher air change rates in clinical spaces. As a result, a series of tests were conducted in an actual hospital to observe the containment and removal of respirable aerosols (0.5-10 µm) with respect to ventilation rate and directional airflow in a general patient room, and, an airborne infectious isolation room. Higher ventilation rates were not found to be proportionately effective in reducing aerosol concentrations. Specifically, increasing mechanical ventilation from 2.5 to 5.5 ACH reduced aerosol concentrations only 30% on average. However, particle concentrations were more than 40% higher in pathways between the source and exhaust as was the suspension and migration of larger particles (3-10 µm) throughout the patient room(s). Computational analyses were used to validate the experimental results, and, to further quantify the effect of ventilation rate on exhaust and deposition removal in patient rooms as well as other particle transport phenomena.

Detection and Measurement of Unhealthy, Environment-Derived Aerosol Materials in an Emergency Department.

OBJECTIVE: To measure unhealthy aerosol materials in an Emergency Department (ED) and identify their sources for mitigation efforts. BACKGROUND: Based on pilot findings of elevated ED particulate matter (PM) levels, investigators hypothesized that unhealthy aerosol materials derive from exogenous (vehicular) sources at ambulance receiving entrances. METHODS: The Aerosol Environmental Toxicity in Healthcare-related Exposure and Risk program was conducted as an observational study. Calibrated sensors monitored PM and toxic gases at Ambulance Triage Exterior (ATE), Ambulance Triage Desk (ATD), and control Public Triage Desk (PTD) on a 3/3/3-day cycle. Cassette sampling characterized PM; meteorological and ambulance traffic data were logged. Descriptive and multiple linear regression analyses assessed for interactions between aerosol material levels, location, temporal variables, ambulance activity, and meteorological factors. RESULTS: Sensors acquired 93,682 PM0.3, 90,250 PM2.5, and 93,768 PM5 measurements over 366 days to generate a data set representing at least 85.6% of planned measurements. PM0.3, PM2.5, and PM5 mean counts were lowest in PTD; 56%, 224%, and 223% higher in ATD; and 996%, 200%, and 63% higher in ATE, respectively (all p < .001). Qualitative analyses showed similar PM compositions in ATD and ATE. On multiple linear regression analysis, PM0.3 counts correlated primarily with location; PM2.5 and PM5 counts correlated most strongly with location and ambulance presence. PM < 2.5 and toxic gas concentrations at ATD and PTD patient care areas did not exceed hazard levels; PM0.3 counts did not have formal safety thresholds for comparison. CONCLUSIONS: Higher levels of PM were linked with ED ambulance areas, although their health impact is unclear.

Mechanical factors affecting nebulized albuterol aerosol particle sizes for asthma drug delivery.

BACKGROUND: Nebulized particles must have diameters between 1 to 5 µm (optimal particle size range [OPSR]) to be deposited in the lower respiratory tract. The purpose of this study is to determine factors that affect the particle size distributions of nebulized albuterol. METHODS: We used a sophisticated laser diffraction machine to measure aerosol particle size distributions. We compared the percentage of particles in the OPSR at different flow rates through single-use disposable (SUD) and semipermanent nebulizers at different flow rates under different conditions. RESULTS: The SUD nebulizer produced OPSR percentages of 16%, 28%, 40%, 50%, 56%, and 62% at 3, 4, 5, 6, 7, and 8 Liters per minute (Lpm), respectively. The semipermanent nebulizer, however, produced OPSR percentages of 57%, 57%, 60%, and 64% at 3, 4, 5, and 6 Lpm, respectively. The home pump produced a gas flow rate of 5.2 Lpm through the SUD nebulizer and 4.2 Lpm through the semipermanent nebulizer. Single-use disposable nebulizer performance did not degrade with use up to 150 nebulizations. Optimal particle size range percentages did not change significantly with large or small nebulization volumes. CONCLUSION: Single-use disposable nebulizers do not degrade with use, but their performance is highly dependent on gas flow rates. At the flow rate achieved by the home pump, the semipermanent nebulizer performs better than the SUD nebulizer.

Principle considerations for the risk assessment of sprayed consumer products.

In recent years, the official regulation of chemicals and chemical products has been intensified. Explicitly for spray products enhanced requirements to assess the consumers'/professionals' exposure to such product type have been introduced. In this regard the Aerosol-Dispensers-Directive (75/324/EEC) with obligation for marketing aerosol dispensers, and the Cosmetic-Products-Regulation (1223/2009/EC) which obliges the insurance of a safety assessment, have to be mentioned. Both enactments, similar to the REACH regulation (1907/2006/EC), require a robust chemical safety assessment. From such assessment, appropriate risk management measures may be identified to adequately control the risk of these chemicals/products to human health and the environment when used. Currently, the above-mentioned regulations lack the guidance on which data are needed for preparing a proper hazard analysis and safety assessment of spray products. Mandatory in the process of inhalation risk and safety assessment is the determination and quantification of the actual exposure to the spray product and more specifically, its ingredients. In this respect the current article, prepared by the European Aerosol Federation (FEA, Brussels) task force "Inhalation Toxicology", intends to introduce toxicological principles and the state of the art in currently available exposure models adapted for typical application scenarios. This review on current methodologies is intended to guide safety assessors to better estimate inhalation exposure by using the most relevant data.

Validation and application of an HPLC-CAD-TOF/MS method for identification and quantification of pharmaceutical counterions.

A generic approach for the analysis of counterions of pharmaceutical reference substances, which are established by the laboratory department of the European Pharmacopoeia (Ph. Eur.), was developed. A mixed-mode chromatography method using charged aerosol detection (CAD) published by Zhang et al. separating 25 commonly used pharmaceutical counterions was selected for this purpose. The method was validated in terms of specificity, repeatability, limits of quantification (LOQs), linearity and range according to ICH guideline Q2(R1) and the Technical Guide for the Elaboration of Monographs of the Ph. Eur. Moreover, the applicability of the method for the purpose of counterion identification and quantification in drug substances as well as for the control of inorganic ions as impurities was demonstrated using selected examples of Ph. Eur. reference standards and other samples of substances for pharmaceutical use (e.g. cloxacillin sodium, somatostatin). It was shown that for identification purposes of the parent substance as well as organic ions the chromatographic system can easily be coupled to a mass selective detector without any modification.

Realization of radioactive equilibrium in the KRISS radon chamber.

The maintenance of radioactive equilibrium between radon and its decay products in a radon chamber is necessary to calibrate radon decay product monitors. In this study, the activity concentrations of radon decay products have been measured, and mosquito-repellent incense has been used to produce aerosol particles in the chamber. Filter papers with 8 µm pore size were used to collect aerosol in the chamber. The activity concentrations of radon decay products have been evaluated by the Modified Tsivoglou Method. The correction factors due to the differences in counting time requirements of the Modified Tsivoglou Method and the time delay between consecutive measurements have been determined. Finally, the radioactive equilibrium has been confirmed by applying the Bateman equation.

Calibration of the KRISS reference ionization chamber for certification of ²²²Rn gaseous sources.

A primary measurement system for gaseous (222)Rn based on the defined solid angle counting method has recently been constructed at KRISS and the reference ionization chamber used to measure the activities of gamma-emitting single radionuclides was adopted as a secondary standard for gaseous (222)Rn. A 20 mL flame-sealed glass ampoule source from the primary measurement system was used to calibrate the ionization chamber for (222)Rn. The (222)Rn efficiency of the ionization chamber was compared with that calculated by using a photon energy-dependent efficiency curve and that measured by using a standard (226)Ra solution. From the comparisons we draw the conclusion that the reference ionization chamber for gamma-emitting radionuclides can be a suitable secondary measurement system for gaseous (222)Rn sources.