NIOSH identified the stakeholder groups that have a vested interest in infection control, emergency response, PPE protections, and/or stockpiling and coordinated with these stakeholders throughout information gathering and decision-making. NIOSH’s National Personal Protective Technology Laboratory (NPPTL) established a PPE Stockpile Partnership, constituted with relevant stakeholder groups including:

Federal entities and stockpiles—The Centers for Disease Control and Prevention (CDC) Influenza Coordination Unit, CDC’s Deputy Director for Infectious Diseases, The Department of Health and Human Services (HHS) Strategic National Stockpile (SNS), the Occupational Safety and Health Administration, the US Department of Veterans Affairs, and the Food and Drug Administration.

Here, policymakers are defined as those organizations responsible for (1) developing national and state emergency response strategies, (2) setting product performance and quality requirements, (3) establishing quality assurance guidance for stockpile facilities, and (4) setting hospital requirements. Product makers include not only the manufacturers but also the product component and material suppliers and developers. The stockpile managers include those who perform supply chain activities (eg, sets inventory levels, selects PPE for purchases, and rotates PPE as needed) for local, state, hospital, and federal facilities.

As part of the NIOSH PPE Stockpile Partnership, NPPTL reached out to various CDC work units with a role in emergency response, and to the strategic national stockpile to identify those PPE types that have been associated with shortages. With input from the Partnership members, APRs and Level 3 and 4 surgical gowns were selected to be included in this study because they are stockpiled in large quantities and serve a critical protective function during high consequence events. Recent shortages associated with air-purifying respirators (APRs) during public health emergencies have been well-documented.^9,10 Additionally, surgical gowns are generally stockpiled to protect workers from blood-borne pathogens and infectious diseases during an epidemic or pandemic. The American National Standards Institute/Association for the Advancement of Medical Instrument PB70 Level 3 gowns are used for moderate risk to the HCP (eg, during blood draws, inserting intravenous IV lines), and Level 4 gowns are used for high risk to the HCP (eg, during long, fluid intense procedures and surgeries).²¹

Isolation gowns were considered by the Partnership members; however, the consensus-based standards for this type of PPE have recently changed thereby making products available to be used as controls for this study manufactured to a different performance specification than the stockpiled products. Therefore, isolation gowns were excluded from the eventual empirical study.

To seek collaborating stockpile facilities, NPPTL solicited nationwide input through a published Federal Register Notice requesting US stockpile facilities to provide information about their facility conditions and inventories, specifically for APRs and surgical gowns.²² Some stockpile managers provided detailed inventory information (eg, model type, quantity, manufacturer year, and storage time), where others only provided model type and/or quantity. Stockpile managers willingly provided their perspective of their facility storage conditions through descriptions or by pictures, as well as providing their inventories to help the researchers with prioritizing collaborating sites. The described approach identified a total of 39 different stockpile facilities that provided either storage condition and/or inventory data, including 13 local, 5 hospital, 11 state, and 10 federal spread across all 10 Department of Health and Human Services (HHS) regions (Fig 1). Contact information for each facility was obtained. Although, many additional facilities are expected to exist across the United States, this marks a significant step forward in identifying common PPE inventories and storage conditions across many facilities. Additionally, identifying this number and variety of facilities provided the opportunity to solicit additional collaborating facilities likely to have disparate storage conditions (environmental and inventory) to include in the study and conduct site visits.

Each collaborating facility provided information for their facility related to topics such as PPE inventory and storage conditions (Appendix Table A1). The 10 HHS geographic regions were targeted, as these regions are often used for regional emergency planning.

With consideration to resources, NIOSH identified 10 stockpile facilities to visit between August 2017 and January 2019, where selection was based on consideration for disparate storage conditions, but common APR and surgical gown inventories. Prior to visiting these facilities, NIOSH devised a series of checklists to facilitate visual inspections of the facility, including site, pallet, case, box, and product inspections. The checklists (Tables A2–A5) focused on environmental parameters perceived to be most relevant to PPE performance based on input from stockpile managers and product manufacturers. The checklists were used to document (1) the presence of dust on PPE packaging, shrink-wrapping, proximity of chemicals to packaging, and moisture; (2) exposure to sunlight and direct light; (3) proximity to fans, windows, doors, and ventilation systems; (4) damage to pallet and product packaging; and (5) location of pallet on storage rack (eg, top, bottom) and location of PPE product on pallet (eg, top/not load-bearing, bottom load-bearing). These checklists were preliminarily tested by NIOSH researchers in a large open room with example PPE product packaging. NIOSH researchers evaluated the checklist for clarity, consistency between evaluators, and efficiency. Draft checklists were then presented to the Partnership members for technical input.

To ensure that its facility sample was diversified, NIOSH used a 3-level stratified sampling strategy based on technical input received from members of NIOSH’s PPE Stockpile Partnership. The strategy leveraged the environmental storage condition data provided by the stockpile managers to select facilities with a range of temperature and humidity conditions, including those that:

Had a well-controlled environment, demonstrated through available temperature and/or humidity data

The first 3 stockpiles visited were strategically selected based on preliminary discussions with the stockpile managers to identify those stockpiles that had a range of the storage conditions listed above.

Using the checklists from each facility, a stratified matrix of potential environmental conditions was developed to better describe site conditions (Table 1). This form allowed the calculation of a “facility environmental condition score” which could be used in the analysis of the empirical data. Temperature and percent relative humidity (%RH) data for stockpiles lacking this data was collected using data-loggers left in the facility for 1 year or by using facility-maintained climate records when available. Storage conditions are dependent on the PPE type and model. Generally for filtering facepiece respirators, manufacturer-recommended temperature and %RH storage conditions are to stay above 4°F and below 95°F and below 80%RH, respectively,²³ but stockpile managers must also take into account the different types and models of PPE, as well as medications that may also be stockpiled.

During the 2017 Partnership Kick-Off meeting with the NIOSH PPE Stockpile Partnership, NIOSH proposed the PPE types to be included and an appropriate strategy for assuring the diversity of stockpile facilities to be included in the study. The 10 HHS geographic regions were targeted, as these regions are often used for regional emergency planning. NIOSH’s sample of facilities were geographically dispersed across the United States, had various levels of oversight, and varied in terms of local climate considerations and facility temperature and %RH levels. Geographical distribution of the 39 facilities included in this study occurred are shown in Figure 1. Ten facilities were selected to participate in site visits, noted by the “*” in Figure 1. These facilities were spread across the HHS regions and varied regarding oversight with one facility being federal, 2 being regional, 6 being state, and one being county-level. There were differing levels of resources available to manage these facilities and various climate conditions were expected to result in disparate environmental conditions within these facilities. A team of NIOSH researchers visited these 10 facilities to document the environmental conditions using the checklists previously described, where a general description of each of the 10 facilities can be found in NIOSH’s PPE conformity assessment studies and evaluations (PPE CASE) Report.²³

The 10 stockpile facilities identified were preliminarily categorized into the following categories:

Controlled environment, demonstrated through available temperature and/or humidity data (n = 3 facilities);

This 3-level stratified sampling strategy substantially increased NIOSH’s confidence that the facilities selected for site visits would reflect disparate temperature and humidity conditions; however, the extent of the differences for these conditions and other relevant conditions (eg, dust, light, and moisture) remained unknown until site visits were conducted at all 10 facilities using the developed checklists. For each of the 6 environmental characteristics (ie, light, dust, protective packaging, chemical spills, moisture, and weight/force), NIOSH established 3 classification levels to capture the variability in conditions that were observed during its site visits. NIOSH then applied the classification scheme to each of the 10 facilities to document the spread of environmental conditions expected to exist in US stockpiles.

In conjunction with these site visits, NIOSH also obtained detailed inventory data (eg, product model, manufacturing year, years in storage, and quantity) for each site. Examples of environmental conditions with potential to affect stockpiled PPE performance are discussed below.

Some facilities had skylight windows that directly shined on the pallets with stockpiled PPE, while other facilities had fluorescent lights directly above the pallets; only the pallets on the top shelving were directly affected. Many facilities left the lights off except when activated by motion sensors other facilities shared the warehouse with other entities, and therefore lights were on in at least half of the warehouse on a regular basis.

Nine of the 10 facilities used pallets to secure PPE within the same lot or model, where one facility used Rubbermaid containers instead of pallets, where individual respirator boxes were sitting on top of the containers; no dust was observed on these respirator boxes. Other facilities had shrink-wrap around the sides of the pallet but not the top (allowing dust to settle on the tops of the pallet boxes), and other facilities had shrink-wrap around the sides of the pallet and the top. Two facilities used a heavy plastic pallet cover to go over each pallet, minimizing dust settlement on product packages. Minimal dust was found on individual PPE boxes, and none was found on the individual PPE itself.

None of the facilities showed evidence of large chemical spills that could have contacted the PPE containers. More localized chemical exposures resulted from pesticide control spraying (inside and outside the facility), annual floor cleaning using industrial cleaners, and pesticide/rodent traps. Moisture damage was observed on some PPE containers and around one wall of a physically substandard warehouse.

Some facilities stacked pallets directly on top of each other with no shelving metal between pallets, resulting in the weight of over 4 pallets on the bottom pallet. Other facilities separated each pallet with metal shelving. At one facility, an entire pallet that was not separated by metal shelving toppled over onto the floor. Within pallets, damage to the external PPE case was found on multiple cases, likely from how tight the shrink-wrap was applied.

A summary of the temperature and %RH data collected from the 10 stockpile facilities is shown in Figures 2 and 3, respectively. There was considerable variance between stockpiles on the control or monitoring of temperature and/or humidity—ranging from a person recording data by hand monthly to computer-prompted notifications and hourly data recording. Some of the stockpiles shared space with other groups that would verbally communicate if the facility had a major problem, but not know more specific details if the facility went out of temperature or humidity range. Although some sites monitored for humidity, no one controlled for humidity beyond ambient geographic climate or building architecture. Facilities that also stored medications had air-conditioning/heating capabilities. Other control measures included evaporative coolers, HVAC filtering, and large and small ceiling fans. One facility stored APRs in a trailer that was outside year-round (the respirators were more recently moved to the basement of a health department); the appearance of mold was found on these APR boxes.

Many facilities that controlled temperature had back-up power generation systems that were relied upon if the air-conditioning/heating unit failed. Accompanying the robust environmental control systems, some stockpiles maintained documentation of temperature and %RH to demonstrate that PPE was kept within prespecified standards over time. The control systems in place at these facilities were robust enough that large temperature and %RH deviations occurred infrequently. Other facilities were unable, due to lack of funding or resources, to continuously maintain an ideal temperature and humidity within the storage environment. Stockpile managers reported that lapses in environmental control could be due to system maintenance issues or a failure in the primary power system without having back-up power systems available. These lapses resulted in numerous instances in which temperature and/or humidity spiked outside of general manufacturer-recommended values for APR and surgical gowns. In some instances, stockpile managers also reported less than adequate system quality could lead to similar spikes during specific times of the year. Other stockpile facilities did not have the technology in place to continuously monitor or regulate temperature and %RH and were located in geographic regions likely to experience temperature and humidity extremes. This combination of circumstances resulted in frequent deviations from ideal storage conditions over time. Where facilities did not actively monitor temperature and humidity, NIOSH researchers left data loggers to log temperature and humidity values every hour for 1 year.

When selecting the stockpile sites for inclusion in the next phase of this study (ie, testing sampled APRs and gowns), it was important to identify collaborating sites with disparate conditions and APR and Level 3 and 4 surgical gown inventories that were consistent with the inventories at other sites. General inventory information (eg, manufacturer/model) was provided from stockpile managers representing 29 stockpiles, with thirty-one¹ different APR models stored across these stockpiles. Out of the 31 models, 3 models were elastomeric half facepieces for use with P95 cartridges, one model was a P95 filter cartridge, and the remaining 27 were N95 filtering facepiece respirators. Detailed inventory information was provided for 20 of these 29 stockpiles—for example, years in storage, quantity, and/or expiration date (if applicable).

The detailed inventory data from these 20 stockpiles, accounting for approximately 53 million APRs, were aggregated. Figure 4 shows these APRs broken down by model and quantity with inventory data from the 10 stockpiles visited by NPPTL researchers noted. Across the entire dataset, the most frequently reported APR models were the 3M 1860/3M 1860S (~52%), Kimberly Clark (KC) 46827/46727 (~17%), and the 3M 8000 (~10%). Ninety-five percent of the APR inventory was captured by 22 product models, all of which were found in at least 1 of the 10 stockpiles visited by NIOSH researchers. Other APR models existed at 14 of the stockpiles and included other 3M and KC models as well as models manufactured by Gerson, Moldex, North², Sperian/Willson, and Cardinal Health.³ Less than 1% of the APR models were elastomeric half facepiece respirators (n = 69,072) and included the 3M 6100, 3M 6200, and the 3M 6300—the corresponding 3M 2071 P95 cartridge filters for these elastomeric half facepiece respirators (n = 377k) were also stockpiled.

Looking at the aggregated dataset, only 12 stockpile managers provided information related to storage time. Of these 12 stockpiles, less than 1% (n = 88.1k) of the cumulative APR inventory were stored ≤5 years of storage, 69% (n = 35.8 million) were stored for 5–10 years, and 26% (n = 13.9 million) were stored for ≥10 years.

Limited inventory data was available for surgical gowns. Of the 29 stockpile managers who provided inventory information, only 15 facilities indicated that they stockpiled Level 3 and/or Level 4 surgical gowns but only 10 of these 15 stockpile managers provided detailed quantity and/or storage time information. Five different gown products were represented once model numbers distinguishing different sizes (eg, L or XL) are combined:

Medline Proxima Aurora Level 3—most frequent (92%; n = 87,074, and 7 stockpiles) with storage times of 0–5 years (one stockpile), 5–10 years (3 stockpiles), and ≥10 years (3 stockpiles)

All but the KC Ultra surgical gowns were stored in at least 1 of the 10 stockpiles visited.