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.

Although the two concepts of lean and sustainable construction have been developed due to different incentives, and they do not pursue the same exact goals, there exists considerable commonality between them. This paper discusses the potentials for integrating the two approaches and their practices and how the resulting synergy from combining the two methods can potentially lead to higher levels of fulfilling the individual goals of each of them. Some limitations and challenges to implementing the integrated approach are also discussed. Based on a comprehensive review of existing papers related to sustainable and lean construction topics, the commonality between the two approaches is discussed and grouped in five categories of (1) cost savings, (2) waste minimization, (3) Jobsite safety improvement, (4) reduced energy consumption, and (5) customers’ satisfaction improvement. The challenges of this integration are similarly identified and discussed in the four main categories of (1) additional initial costs to the project, (2) difficulty of providing specialized expertise, (3) contractors’ unwillingness to adopt the additional requirements, and (4) challenges to establish a high level of teamwork. Industry professionals were then interviewed to rank the elements in each of the two categories of opportunities and challenges. The results of the study highlight how future research can pursue the development of a new Green-Lean approach by investing in the communalities and meeting the challenges of this integration.

Certain pathogens are transmitted through air by respiratory droplets that desiccate shortly after emission and form droplet nuclei (Nicas et al. 2005). Droplet nuclei are sufficiently small (<5.0 μm) to remain suspended in air indefinitely and, thus, create a pathway between an infected and susceptible person (Sehulster et al. 2003). This process is called “airborne transmission.” Patients with an airborne infectious disease (e.g., measles, SARS, tuberculosis, varicella, etc.) are isolated from the healthcare environment in an airborne infection isolation room to protect other patients and healthcare workers. These rooms have special features to effectively contain and remove airborne pathogens. For example, a 2.5-Pa negative pressure relationship with adjoining spaces is required for an airborne infection isolation room to create directional airflow into the room and prevent the transmission of airborne pathogens from the airborne infection isolation room to adjacent healthcare spaces. Directional airflow, however, may be disrupted and even reversed by door-opening motion and the movement of people and equipment into and out of the airborne infection isolation room. This article highlights the results of both experimental and computation studies that explore air exchange and particle movement between an isolation room and anteroom relative to 3-, 5-, and 7-s door cycle speeds and between neutral and negative air pressure relationships.