Setting and participants

This study was conducted in the cardiovascular medical ward of a tertiary Grade A hospital in China. Purposive sampling was used to recruit participants with direct experience of SHS exposure and to capture variation in age, sex, household smoking context, and exposure settings. Inclusion criteria were: 1) aged ≥18 years; 2) clinical diagnosis of CHD; 3) self-reported SHS exposure; 4) ability to communicate effectively; and 5) willingness to participate. Participants were excluded if they had severe comorbidities impairing communication, a diagnosed major psychiatric disorder, a current smoking status, or a critical/unstable health condition.

For recruitment, SHS exposure was defined pragmatically as participants’ self-reported recent or repeated exposure to tobacco smoke from other people in daily life, including at home, at work, or in social/public settings. During screening, participants were asked whether they had experienced SHS exposure in their recent daily lives and whether such exposure occurred repeatedly across common living environments. Because this study aimed to explore lived experience rather than quantify exposure dose, no formal quantitative threshold of frequency, duration, or intensity was imposed.

A descriptive phenomenological approach was adopted because the study aimed to understand how patients with CHD experienced and made sense of SHS exposure in everyday contexts, rather than to generate a formal theory or examine social processes at a more abstract explanatory level¹⁷. Sampling proceeded concurrently with data collection and analysis until thematic saturation was reached, defined as the point at which subsequent interviews no longer generated substantively new codes, meanings, or thematic insights but instead mainly confirmed the developing thematic structure¹⁸. A total of 12 eligible patients were approached, and all agreed to participate. Sociodemographic information, smoking history, and CHD history were collected before the interview.

Data collection

Face-to-face interviews were conducted from December 2023 to April 2024. Each interview lasted approximately 30 minutes and was audio-recorded with participants’ consent. Flexible probing was used during interviews to encourage participants to elaborate on their perceptions, exposure situations, bodily sensations, and coping responses. The interview guide was developed from a literature review and refined after pilot interviews with three patients with CHD. The pilot interviews were conducted to improve question clarity, sequencing, and sensitivity and were not included in the final analysis. The interview guide explored: 1) knowledge and information sources about SHS; 2) perceived health impacts; 3) exposure contexts and coping strategies; 4) perceived facilitators and barriers to reducing exposure; and 5) views on smoke-free homes. Interviews were conducted in Chinese; transcripts were analyzed in Chinese, and illustrative quotations were translated into English for reporting. English translations of the quotations were checked by bilingual researchers to preserve semantic equivalence with the original Chinese transcripts.

Ethics

This study was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology in in December 2023 (Approval No. TJ-IRB20231235). Written informed consent was obtained from all participants before the interviews. Participants were informed of the study procedures, their right to withdraw, and the measures taken to ensure confidentiality.

Researcher characteristics and reflexivity

The multidisciplinary research team included nurses specialized in pulmonary and cardiac rehabilitation, and researchers trained in qualitative methods. The primary interviewer had clinical experience in caring for CHD patients but did not provide direct clinical decision-making for enrolled participants. To reduce potential power imbalance, interviews were conducted in a private area of the ward, and participants were reminded that participation or refusal would not affect their care. No prior personal relationship existed between the interviewer and participants before recruitment. Reflexivity was strengthened through field and reflexive notes recorded after each interview, documenting assumptions, emotional responses, and potential leading probes, which were subsequently discussed in regular analytic meetings to support reflexive interpretation.

Data analysis

Recordings were transcribed using the iFlytek Hearing App for initial transcription, followed by manual verification against the audio by two bilingual researchers. Participant identifiers (P1–P12) were used during analysis. Analysis followed the Colaizzi seven-step method: familiarization, extraction of significant statements, formulation of meanings, clustering into themes, exhaustive description, fundamental structure, and verification¹⁹. No dedicated qualitative data analysis software was used. Transcripts were coded manually using Microsoft Word and Excel. Two researchers independently coded an initial subset of transcripts, compared coding decisions, and resolved discrepancies through discussion and repeated checking against the original transcripts until consensus was reached. An audit trail was maintained throughout the analysis. Data collection and analysis proceeded iteratively, allowing insights from earlier interviews to inform subsequent interviewing and analytic focus. Member checking was conducted with three participants who were willing and available to be re-contacted and who reflected variation in participant characteristics and exposure experiences. They were invited to comment on whether the preliminary thematic structure adequately reflected their experiences, and their feedback was used to confirm interpretive credibility and refine wording where necessary. This was undertaken to enhance interpretive credibility rather than to re-contact the full sample. To enhance trustworthiness, we used pilot testing of the interview guide, transcript verification, independent coding, reflexive journaling, audit-trail documentation, and member checking. Reporting followed SRQR, and a completed COREQ checklist was prepared²⁰ (supplementary file).

Participant characteristics

Participant characteristics are presented in Table 1. Of the 12 participants, seven were male, and five were female. Nine participants were ≥60 years. All five female participants reported that their spouses smoked. Among the male participants, most were non-smokers, with one participant reporting a history of smoking.

Themes

Analysis of the interview data generated five interrelated themes: 1) Limited and fragmented understanding of SHS; 2) Difficulty avoiding SHS exposure across everyday settings; 3) Aversion to SHS and sociocultural constraints on speaking up; 4) Reliance on smoke-free policies and their enforcement; and 5) Smoke-free homes as an ideal yet difficult-to-achieve goal. Representative quotations are presented in Table 2.

Theme 1: Limited and fragmented understanding of SHS

Participants generally recognized SHS as harmful, but their understanding was often incomplete, experience-based, and lacking in specificity. Many described SHS in simple sensory or experiential terms, such as smoke exhaled by others or smoke that could be smelled in the air, rather than identifying specific biomedical mechanisms or clearly articulating its health consequences. As one participant explained:

Participants’ awareness of SHS was commonly shaped by fragmented sources, including short videos, television messages, mobile phone content, or stories about illness among relatives and acquaintances. For example, one participant said:

while another stated that she had learned from Douyin (Chinese version of TikTok) that:

At the same time, several participants admitted that although they knew SHS was harmful, they could not clearly explain its specific effects. As one participant put it:

Overall, participants described their understanding of SHS as present but often partial, experience-based, and lacking in specificity.

Theme 2: Difficulty avoiding SHS exposure across everyday settings

This theme focuses on the settings in which SHS exposure occurred and on the practical constraints that made avoidance difficult. Participants described SHS exposure as a pervasive presence embedded in daily life across the home, workplace, and social settings, often leaving them with little room to avoid exposure without disrupting everyday routines or social participation. At work, exposure was frequently associated with limited power to intervene, particularly in hierarchical or cooperative environments. As one participant explained:

At home, exposure often came from smoking spouses or family members, and although some participants attempted to restrict indoor smoking, these efforts were only partially successful. For example, one participant said:

while another noted:

Social spaces such as tea houses and mahjong parlors were also described as common exposure settings, where avoiding smoke sometimes meant withdrawing from participation altogether. As one participant stated:

Even brief public encounters, such as passers-by smoking nearby, were mentioned as further reminders of how difficult SHS was to avoid in everyday life. Overall, participants described SHS exposure as occurring repeatedly across multiple everyday settings, with avoidance often constrained by practical and situational factors.

Theme 3: Aversion to SHS and sociocultural constraints on speaking up

In contrast to the exposure contexts described above, this theme concerns participants’ emotional aversion to SHS and the sociocultural barriers to directly confronting smokers. Although participants strongly disliked SHS, many felt constrained in directly asking others not to smoke. Their responses appeared to vary according to their relationship with the smoker, revealing a clear relational gradient. Participants were generally more willing to remind close family members, but were much more hesitant when dealing with guests, elders, acquaintances, or smokers in public settings. One participant explained:

Another stated:

Similarly, a participant noted that when guests smoked at home:

As a result, avoidance became a common coping strategy. Even participants who expressed anger or frustration toward SHS often reported that, in practice, they chose to sit farther away, leave the setting, or remain silent rather than openly challenge smokers. Participants often described a strong aversion to SHS alongside reluctance to speak up, particularly in situations involving politeness, face (i.e. self-image and emotional standing in social interactions) and relational concerns.

Theme 4: Reliance on smoke-free policies and their enforcement

Participants generally perceived that reducing SHS exposure in public settings could not rely on personal reminders alone, and instead depended largely on formal smoke-free policies and their effective enforcement. Several participants described individual efforts to discourage smoking as socially difficult or practically ineffective, especially in hospitals, workplaces, or other shared spaces. One participant commented:

At the same time, participants distinguished clearly between the existence of smoke-free policies and the visible enforcement of those policies. This was reflected in comparisons with places perceived to have stricter management. As one participant noted:

Participants commonly referred to smoke-free policies as important for protection in public settings while also noting variability in enforcement.

Theme 5: Smoke-free homes as an ideal yet difficult-to-achieve goal

Most participants regarded smoke-free homes as desirable and beneficial, particularly for health and household well-being. As one participant stated:

However, although the idea of a smoke-free home was widely supported in principle, participants often described it as difficult to fully achieve in practice. A recurring pattern was that smoking within the household was managed through compromise rather than complete prohibition. One participant commented:

Others described family members smoking in stairwells, balconies, or just outside the home as a way of reducing, but not eliminating, exposure. For instance, one participant said:

while another reported:

Participants commonly described smoke-free homes as partially restricted rather than completely smoke-free, with household smoking practices often managed through negotiation and compromise.

Strengths and limitations

Measures against SHS remain a key challenge. Exposure to SHS is closely associated with coronary heart disease. Even brief exposure to SHS can harm the cardiovascular system, which is particularly sensitive to its toxins, much like the effects of active smoking⁴. These findings underscore the potential relevance of SHS exposure in the broader context of secondary prevention for patients with CHD. This study helps clarify how SHS exposure was perceived, negotiated, and managed among participants in this study context. However, this study has several limitations. First, because the findings were based on retrospective self-reports, recall bias and social desirability bias may have influenced participants’ accounts. Second, purposive sampling within a single tertiary Grade A hospital may have introduced selection bias, favoring participants who were more willing or able to discuss SHS exposure. Third, participants were hospitalized patients with CHD, and their clinical vulnerability may have shaped how they perceived and described SHS-related risk. Fourth, although reflexive journaling and team discussions were used to reduce bias, interviewer characteristics and assumptions may still have influenced data collection and interpretation. Finally, the study was conducted in a specific Chinese healthcare and sociocultural context, and the findings should not be assumed to be directly transferable to other populations or settings. In addition, seasonal variation in SHS exposure was not examined in this study and may be explored in future quantitative or longitudinal research. Future research using multi-site, more diverse, and potentially mixed-methods designs is needed to examine the transferability and broader relevance of these findings.